This is CNBC's live blog tracking developments on the war in Ukraine. See below for the latest updates. 

Ukrainian President Volodymyr Zelenskyy in his latest nightly address to the nation says sanctions on Russia are very significant and economically painful, but still aren't enough for "the Russian military machine to be left without means of subsistence."

Russia appears to be retaliating for the sinking of its flagship missile cruiser Moskva, which Ukrainian forces say they hit with missiles, as explosions are heard in Kyiv. The U.S. now believes Ukrainian missiles sank the Moskva, an official told NBC News.

The loss of such a major naval asset may force Russia to rethink its strategy in the Black Sea, analysts say.

Finland's minister for European affairs says the Nordic country is "highly likely" to join NATO, a move Russia has warned against.

Meanwhile, President Joe Biden says what took place in the Ukrainian town of Bucha was "indisputable evidence of Putin's war crimes everywhere." Ukraine President Volodymyr Zelenskyy, likewise, urged Biden to label Russia a state sponsor of terrorism.

Damage to Ukraine's road infrastructure a significant obstacle in delivering aid, UK’s Defence Ministry says

Ukraine's roads and other infrastructure have been badly damaged by Russian troops, and that is now posing a significant challenge in delivering humanitarian aid to some areas, said the U.K.'s Defence Ministry in its daily intelligence update.

"Road infrastructure in conflict affected areas of Ukraine has sustained significant damage. Russian troops have exacerbated this by destroying bridges, employing land mines and abandoning vehicles along key routes as they withdrew from northern Ukraine," the ministry said in its update, posted on Twitter.

River crossings in and around the northern Ukrainian city of Chernihiv have been destroyed, leaving only one pedestrian bridge in the city, the update said.

"Damage to Ukraine's transport infrastructure now presents a significant challenge in delivering humanitarian aid to areas formerly besieged by Russia," the ministry tweeted.

— Weizhen Tan

Zelenskyy appeals for ‘stronger, more destructive’ sanctions

Ukrainian President Volodymyr Zelenskyy says he's been hearing different predictions about how long the war with Russia will last.

"Some say a few weeks. Others — several years. Some say the war will last until the end of this year. And someone advises to prepare for a permanent confrontation with Russia as long as it exists," he said in his nightly address to the nation.

But Zelenskyy says the "effectiveness of instruments of influence" on Russia used by Ukraine as well as its entire anti-war coalition against Russia must be taken into account, when predicting how long the war will last.

"The success of our military on the battlefield is really significant. Historically significant. But not enough to clean our land from the occupiers yet. We'll beat them more," he said.

"Sanctions against Russia are very significant. Economically painful. But still not enough for the Russian military machine to be left without means of subsistence. We promote stronger, more destructive ones," Zelenskyy said.

These two areas, he says, will determine how long this war will last. The amount of support for Ukraine "literally defines how many more Ukrainians the occupiers will manage to kill."

"If someone says: year or years, I answer: you can make the war much shorter. The more and the sooner we get all the weapons we have requested, the stronger our position will be and the sooner peace will come," he said. "The sooner the democratic world recognizes that the oil embargo against Russia and the complete blockade of its banking sector are necessary steps towards peace, the sooner the war will end."

— Weizhen Tan

UN calls for access to besieged areas, says people are being 'starved to death'

The United Nations is calling for "unimpeded access" to families trapped in besieged areas in Ukraine, saying that people are being "starved to death."

"We're calling on everyone to give us the access we need to reach the people in besieged cities," David Beasley, executive director of the United Nations World Food Program said.

"It's one thing when people are suffering from the devastation of war. It's another thing when they're being starved to death," he added in a statement.

The embattled city of Mariupol is believed to be running out of its last reserves of food and water, the statement said, adding that no humanitarian aid has been allowed into the city since it was besieged two weeks ago.

The food program has delivered food supplies to 1.4 million people in Ukraine so far, aiming to reach 2.3 million people overall this month.

— Weizhen Tan

Ukraine's prime minister, other officials to visit Washington, report says

Ukraine's Prime Minister Denys Shmyhal and the country's finance officials will visit Washington next week during the International Monetary Fund and World Bank spring meetings, Reuters reported, citing sources.

Shmyhal, Finance Minister Serhiy Marchenko and central bank governor Kyrylo Shevchenko are set to meet with finance officials from the Group of Seven countries and others, Reuters reported.

The economic impact of the Russia-Ukraine war is expected to take centerstage at next week's meetings, with the IMF also expected to downgrade its global growth forecast because of the conflict, the report said.

— Weizhen Tan

Zelenskyy says 2,500 to 3,000 soldiers Ukrainian soldiers have been killed

About 2,500 and 3,000 Ukrainian soldiers have been killed and 10,000 injured since Russia's invasion of the nation, Ukrainian President Volodymyr Zelenskyy said during in an interview with CNN, snippets of which aired Friday.

Ukraine estimates the Russian military's casualties at 19,000 to 20,000 given the information available, he said. Cut-off communication channels across Ukraine make it difficult to tally the total civilian losses, he added.

Numbers released Friday by the Office of the U.N. High Commissioner for Human Rights peg the civilian casualties at 2,000 since the war in Ukraine began. Meanwhile, recent numbers from Ukrainian officials suggest 18,600 Russian soldier deaths, while three-week-old NATO estimates suggest up to 15,000 losses. Russia confirmed 1,351 soldier deaths last month.

As civilian casualties in Ukraine pick up, Zelenskyy lamented the suffering of his people.

"It is great pain for me," he said. "I can't watch it as a father only because all you want after this is revenge and to kill. I have to watch as the president of a state where a lot of people have died and lost their loved ones and there are millions of people who want to live. All of us want to fight, but we all have to do our best for this war not to be endless."

Meanwhile, Zelenskyy said the sinking of a Russian warship was "not a tragedy" but a tool that makes the Russian Federation "less capable" of attacking Ukraine.

"This is important and about what happened to it, the history will tell," he said.

— Samantha Subin

Regional governor says Mariupol 'has been wiped off the face of the Earth'

Russia's attack on the city of Mariupol has reduced the city to nothing but rubble, Pavlo Kyrylenko, governor of the Donetsk region told CNN on Friday.

"The enemy cannot seize Mariupol," he said. "The enemy may seize the land that Mariupol used to stand on but the city of Mariupol is no more. The city of Mariupol has been wiped off the face of the Earth by the Russian Federation."

The comments come as Russia claims advances in its siege of Mariupol and weather conditions have stalled the movement of military vehicles. With a major battle likely to occur within the next several days, Kyrylenko said he has urged civilians to evacuate.

Russian forces aim to capture Mariupol to create a land bridge to Crimea, a plan Kyrylenko called an "illusion."

— Samantha Subin

Zelenskyy urges Biden to identify Russia as a state sponsor of terrorism

During a recent phone conversation, Ukrainian President Volodymyr Zelenksyy asked President Joe Biden to label Russia a state sponsor of terrorism.

The Washington Post first reported the news, which was later confirmed to NBC News by two sources familiar with the matter.

Adding Russia to the U.S. list — which currently includes Iran, North Korea, Syria and Cuba — would prompt harsher sanctions on the country.

The sources told NBC that the Biden administration is currently prioritizing pleas for weapons and energy sanctions over Zelenksyy's request.

— Samantha Subin

About 2,000 civilians deaths confirmed in Russian invasion, UN says

Almost 2,000 civilians have been killed since the start of Russia's war on Ukraine, the Office of the U.N. High Commissioner for Human Rights said Friday.

In a release, the office said it has documented 1,982 deaths between Feb. 24 and April 14, but it believes the tally is "considerably higher."

"OHCHR believes that the actual figures are considerably higher, as the receipt of information from some locations where intense hostilities have been going on has been delayed and many reports are still pending corroboration," the release said.

Ukraine's Ministry of the Interior says at least 2,700 civilians had been killed, the UN added.

The use of explosive weapons including heavy artillery shelling caused most of the deaths, the office said. At least 70 of those killed were children and 2,651 civilians have been injured since the war began.

— Samantha Subin

U.S. believes Ukrainian missiles sank Russian warship

The U.S. now believes that two Ukrainian Neptune missiles caused the Russian warship Moskva to sink, a senior Defense official told NBC News.

It's not clear why the ship's defenses didn't kick in, the official told NBC News, although there could have been several factors at work, including maintenance issues.

The official also said that the U.S. doesn't know whether a drone might have distracted the Russian ship's air defenses.

– Mike Calia

More than 900 civilian bodies found near Kyiv, police say

A Ukrainian police official said more than 900 civilian bodies have been found near Kyiv as Russian forces have withdrawn from the region.

Kyiv's regional police chief Andriy Nebytov said two mass graves were discovered in Bucha, outside the capital of Kyiv, with 97 bodies. At least 95% of the victims were shot.

"Bucha has the highest number of casualties, which means that the occupiers operating in Bucha were the most brutal," Nebytov said during a Friday briefing translated by NBC News. "We have already taken more than 350 bodies from the city."

— Samantha Subin

Ukraine says fighting rages around Mariupol steel plant, port

Ukraine said on Friday it was trying to break Russia's siege of Mariupol and that fighting raged around the southern city's Illich Steel and Iron Works and port.

"The situation in Mariupol is difficult and hard. Fighting is happening right now. The Russian army is constantly calling on additional units to storm the city," defense ministry spokesman Oleksandr Motuzyanyk said.

"But as of now the Russians haven't managed to completely capture it," he told a televised briefing.

Motuzyanyk said Russia had used long-range bombers to attack Mariupol for the first time since its Feb. 24 invasion, and that elsewhere Russian forces were concentrating efforts on seizing the cities of Rubizhne and Popasna in Ukraine's east.

Russia said on Friday that it had taken full control of Mariupol's Illich Steel and Iron Works and pledged more strikes on targets in Kyiv.

— Reuters

Russia's use of weapons of mass destruction would have "cascade of consequences," says State Department spokesperson

The use of weapons of mass destruction by Russia could bring a "cascade of consequences" from the U.S. and its allies, State Department spokesman Ned Price told CNN's "At This Hour."

"I'll say a couple things, both of which shouldn't have to be said in the year 2022," Price said. "Number one, the use of any kind of weapon of mass destruction ... would constitute the height of irresponsibility. And number two, the use of WMD would elicit a cascade of consequences not only from the United States but from our partners and allies around the world."

The U.S. government is consistently monitoring Russia's "nuclear posture" but does not currently see a need to shift its nuclear position, Price added.

— Samantha Subin

Russia tells U.S. to stop providing weapons to Ukraine

Russia sent a formal diplomatic letter to the U.S., warning of "unpredictable consequences" if the country continues to arm Ukraine, The Washington Post first reported.

"We call on the United States and its allies to stop the irresponsible militarization of Ukraine, which implies unpredictable consequences for regional and international security," the letter reportedly said, noting that continued deliveries of "most sensitive" weapons systems were "adding fuel" to the ongoing conflict.

It comes after President Joe Biden earlier this week approved another $800 million in military assistance for Ukraine to upgrade its artillery systems following an appeal from Ukrainian President Volodymyr Zelenskyy.

A White House official who has seen the diplomatic note and the report confirmed its content to NBC News, saying the letter is a signal that weapons deliveries are "making a difference." The official added that Russia has previously complained about U.S. support for Ukraine, and while the White House is taking the note seriously it is not seen as particularly "threatening."

"What we can confirm is that, along with allies and partners, we are providing Ukraine with billions of dollars worth of security assistance, which our Ukrainian partners are using to extraordinary effect to defend their country against Russia's unprovoked aggression and horrific acts of violence," a State Department spokesperson said but would not confirm the correspondence.

— Samantha Subin

U.S. ambassador says Poland is 'feeling the pressure' of 4 million Ukrainian refugees

Mark Brzezinski, the U.S. ambassador to Poland, told MSBC's "Morning Joe" that the country has taken in roughly 4 million Ukrainian refugees since Russia's unprovoked attack on Ukraine began on Feb. 24, noting that 10% of Poland's population today is Ukrainian refugees.

"The system is both embracing these refugees, it has capacity, but it is also beginning to weigh down the system," Brzezinski said. "The hospitals, the schools, are feeling the pressure of half a million new students as we go into the spring semester."

He said that while most refugees have been placed in the nation's largest cities, "the government wants to place the refugees that are continuing to come in, in the rural areas, and many of those refugees would much prefer to be in the cities."

He also said, "the fact is that most of the refugees that have come to Poland want to stay in Poland," rather than continuing on to the U.S., for example. He explained that the Polish language and food are similar to Ukraine's, and also that "there is a proximity that allows the refugees to hope that they can return home and to start rebuilding."

Brzezinski said he worries that Russian President Vladimir Putin could expand his aggression beyond Ukraine and make the war a "regional conflict," especially in light of the reaction by Russian authorities to the prospect of Sweden and Finland joining NATO.

Disclosure: MSNBC and CNBC are divisions of NBCUniversal.

— Michele Luhn

Ukraine says 9 humanitarian corridors agreed to open Friday

Nine humanitarian corridors to evacuate civilians are slated to open Friday, Ukraine's Deputy Prime Minister Iryna Vereshchuk wrote in a Telegram post.

The corridors will allow people to evacuate from Mariupol, Berdyansk, Tokmak and Energodar to Zaporizhia, a city in southeastern Ukraine. Civilians can access the corridors using their own means of transportation.

Five routes are also expected to open for civilians to access Bakhmut, in eastern Ukraine.

— Samantha Subin

Recaptured Ukrainian village left with wrecked tanks, bodies and questions

As Russian forces pull back after failing to take major cities including Kyiv and Kharkiv to refocus their offensive on the Donbas region in the southeast, residents of the surrounding areas are beginning to clean up after weeks of occupation.

Residents in a recaptured east Ukrainian village have been left with mashed tanks in the mud, destroyed buildings and mourning families.

Ukrainian soldiers last month retook Husarivka, an agricultural village with a peacetime population of 500-600 around 75 miles southeast of Kharkiv city, after heavy fighting following the Russian invasion on Feb. 24.

— Reuters

Ukraine says Russia used long-range bombers on Mariupol; 1st time in war

Ukraine's defense ministry spokesman Oleksandr Motuzyanyk said on Friday that for, the first time since the start of its invasion, Russia used long-range bombers to attack the besieged port city of Mariupol.

Motuzyanyk said Russia was concentrating its efforts on seizing the cities of Rubizhne, Popasna and Mariupol.

— Reuters

Zelenskyy praises Ukrainians' bravery on day 50 of Russia's invasion

Ukrainian President Volodymyr Zelenskyy praised his people's bravery and resilience on the 50th day of Russia's invasion, saying, "We have withstood 50 days already. Fifty days of Russian invasion, although the occupiers gave us a maximum of five."

He called the invasion "suicidal" and "absurd", speaking in his latest national address.

When the invasion began, "No one was sure that we would withstand it ... Many of them advised me to flee the country. Advised to actually surrender to tyranny," Zelenskyy said.

"But they didn't know us either. And they did not know how brave Ukrainians are, how much we value freedom. Our opportunity to live the way we want."

"50 days of our defense is an achievement. Achievement of millions of Ukrainians," he said. "Everyone who made the main decision in life on February 24 - to fight. To be human. Not to give up. And not to betray."

— Natasha Turak

Russia has now lost of its two major naval assets, UK's Defence Ministry says

Russian forces have now lost two important naval vessels in Ukraine, the U.K.'s Defence Ministry said in its daily intelligence updated posted to Twitter, following the sinking of the Moskva on Thursday.

"Russia has admitted that the Slava-class cruiser Moskva has sunk. As flagship of Russia's Black Sea Fleet, the Moskva served a key role as both a command vessel and air defence node," the ministry said.

"This incident means Russia has now suffered damage to two key naval assets since invading Ukraine, the first being Russia's Alligator-class landing ship Saratov on 24 March," it added. "Both events will likely lead Russia to review its maritime posture in the Black Sea."

— Natasha Turak

Moody's says Russia may be in default

Ratings agency Moody's says Russia may be in default as it attempted to service its dollar bonds in rubles. If that becomes the case, it would be Russia's first large-scale default on foreign debt since the Bolshevik Revolution in 1917.

Russia made payments on April 4 on two bonds maturing in 2022 and 2024 in rubles, despite the terms of the securities requiring payment in dollars. Moscow says any default is forces upon it by the West because of its sanctions.

Russia "therefore may be considered a default under Moody's definition if not cured by 4 May, which is the end of the grace period," Moody's said in a statement. "The bond contracts have no provision for repayment in any other currency other than dollars."

Finance Minister Anton Siluanov told local media previously that Russia will take legal action if forced to default on its debt.

— Natasha Turak

Russia warns missile strikes on Kyiv will increase in response to attacks 'on Russian territory'

Russia warned of more missile strikes on Kyiv, a day after the sinking of its flagship naval vessel Moskva in the Black Sea, which Ukrainian forces say they hit with their own missiles.

"The number and scale of missile strikes on targets in Kyiv will increase in response to any terrorist attacks or acts of sabotage on Russian territory committed by the Kyiv nationalist regime," Russia's Defense Ministry said in a statement. Moscow has not accepted Ukraine's claim to having struck its ship, and maintains that it sunk due to a fire onboard.

Russia says its forces have hit 13 military facilities around Ukraine overnight, and that its S-400 air defense system shot down a Ukrainian helicopter near Chernigov. Russia's military says Ukraine carried out an attack on a Russian village via helicopter on Thursday. NBC has not been able to verify these claims.

Explosions hit Kyiv on Friday, the largest in some two weeks, which Russia says targeted a facility making and repairing Ukrainian missiles. A worker at a car repair shop in Kyiv told Reuters he saw three blasts hit an industrial building across the street from him, starting a fire that was put out by firefighters.

"The building was on fire and I had to hide behind my car," Kirill Kyrylo told the news agency.

— Natasha Turak

Finland 'highly likely' to join NATO, minister says

Facing a dramatic change in its security assessment and relations with Russia, Finland is 'highly likely' to join NATO now, Finland's European affairs minister Tytti Tuppurainen told Sky News in an interview.

"The people of Finland seem to have already made up their mind and there is a huge majority for NATO membership of Finland," she said from Helsinki."

"Of course, that's not all. We are a parliamentary democracy so we need to discuss this issue in our parliament. At this point I would say it is highly likely, but a decision is not yet made."

Russia has warned of consequences if the Nordic country makes such a move, and saying it would need to make new nuclear deployments in the Baltics is the alliance expanded along Russia's borders.

— Natasha Turak

Kyiv hit with most powerful explosions heard in weeks

The Ukrainian capital Kyiv was hit Friday with the most powerful explosions heard since Russian forces retreated from the areas around the capital two weeks ago.

Russia said it targeted and hit a plant in Kyiv that made and repaired Ukrainian missiles, including anti-ship missiles. The strikes come a day after Russia's flagship missile cruiser, Moskva, sank in the Black Sea off the Ukrainian coast. Moscow said it was due to a fire on board, while Ukrainian authorities say they struck it with missiles.

— Natasha Turak

Sinking of Moskva will make Russia rethink its Black Sea strategy, British ministry says

The loss of Russia's Black Sea Fleet flagship Moskva is likely to force the Kremlin to review its maritime strategy in the Black Sea, according to a Western assessment.

Ukraine said that it struck the Moskva on Wednesday with two cruise missiles. Moscow admitted that the missile cruiser Moskva sank on Thursday, but blamed it on onboard ammunition that detonated.

A Pentagon spokesman said on Thursday that the United States could confirm neither story.

Regardless, the Moskva was Russia's command vessel on the Black Sea, and it was critical to the Russian fleet's air defense strategy, the U.K. Ministry of Defence said in an intelligence assessment posted Friday.

"This incident means Russia has now suffered damage to two key naval assets since invading Ukraine, the first being Russia's Alligator-class landing ship Saratov on 24 March," the Ministry of Defence said.

"Both events will likely lead Russia to review its maritime posture in the Black Sea," the ministry said.

Military analysts have speculated that the Moskva would have played an important role in any amphibious attack on Odesa, Ukraine's most important maritime port.

The Soviet-era Moskva was refitted to improve its capabilities and returned to operational status last year, the British ministry said. It played roles in Russia's bombing of Syria in 2015, its invasion of Crimea in 2014, and its war with Georgia in 2008.

Russia has claimed that its crew of 510 individuals was safely evacuated.

— Ted Kemp

'Indisputable evidence of Putin's war crimes': U.S. lawmakers visit Kyiv and Bucha

Two U.S. lawmakers visited Ukraine on Thursday, becoming the first known American officials to do so since Russia began its offensive on Feb. 24.

Senator Steve Daines (R-MO) and Rep. Victoria Spartz (R-IN), who was born in Ukraine, traveled to there to meet Ukrainian officials in the capital of Kyiv and Bucha, where Russian troops have been accused of mass atrocities.

"There is indisputable evidence of Putin's war crimes everywhere — the images of shallow mass graves filled with civilians, women and children are heart wrenching," Daines said in a statement.

"America and the world need to know about Putin's atrocities against the innocent people of Ukraine now, not after time has passed and the aftermath of evil and bloodshed have been cleaned up. The sooner we can provide Ukraine with the lethal aid they need to win this war, the sooner we will end the war crimes."

The bodies and mass graves were found after Russian troops pulled out of Bucha, a suburb on the outskirts of Kyiv. The atrocities prompted the UN to suspend Russia from its seat on the Human Rights Council and pushed the U.S. and European leaders to impose more sanctions on Moscow.

— Joanna Tan

Read CNBC’s previous live coverage here:

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