This was CNBC's live blog tracking developments on the war in Ukraine.

The Kremlin said Tuesday that Ukrainian President Volodymyr Zelenskyy's latest appeal for more Western aid and involvement in the conflict is due to Ukraine's "extremely unfavorable" situation on the battlefield.

Kremlin spokesperson Dmitry Peskov told reporters that new arms supplies will not change the dynamic on the battlefield either.

In other news, Poland has arrested nine people in connection with acts of sabotage committed in the country on the orders of Russian services.

"We currently have nine suspects arrested and charged with engaging in acts of sabotage in Poland directly on behalf of the Russian services," Polish Prime Minister Donald Tusk told private broadcaster TVN24 late Monday, Reuters reported.

Russia begins exercise with tactical nuclear weapons

Russian forces on Tuesday began the first stage of training in the "preparation and use of non-strategic nuclear weapons," the Ministry of Defense said in a post on Telegram.

"As part of this stage, the personnel of the missile formations of the Southern Military District are practicing combat training tasks of obtaining special ammunition for the Iskander operational-tactical missile system, equipping launch vehicles with them and covertly advancing to the designated position area in preparation for missile launches," the post read.

President Vladimir Putin ordered the drills earlier this month in a move he said was designed to deter military involvement in Ukraine by the West.

— Karen Gilchrist

Russia arrests former army commander on suspicion of fraud

The former commander of Russia's 58th Army, who last year decried the treatment of the military personnel on the battlefield, was arrested on suspicion of large scale fraud, TASS news agency reported Tuesday.

Major General Ivan Popov was ordered by the country's military court to be detained for two months, TASS said. Popov's lawyer said he had appealed the detention, Reuters reported Interfax as saying.

"The ex-commander of the 58th Guards Combined Arms Army, Ivan Ivanovich Popov, was arrested on suspicion of fraud," the agency's interlocutor said, according to TASS.

Last July, Popov said he was dismissed after a four-minute audio message emerged, in which he outlined major shortcomings in Russia's defenses and said they had caused mass casualties among his troops on the battlefield in Ukraine.

— Karen Gilchrist

EU countries adopt plan to use frozen Russian assets for Ukraine's defense

EU countries have formally adopted a plan to use windfall profits from Russian central bank assets frozen in the EU for Ukraine's defense, the Belgian government said on Tuesday.

The text only needed a rubber-stamp by ministers after EU ambassadors reached the agreement in early May.

Under the agreement, 90% of the proceeds will go into an EU-run fund for military aid for Ukraine, with the other 10% going to support Kyiv in other ways.

The EU expects the assets to yield about 15-20 billion euros ($16.30-$21.70 billion) in profits by 2027. Ukraine is expected to receive the first tranche in July, EU diplomats said.

The Group of Seven countries (G7) froze around $300 billion worth of Russian financial assets soon after Moscow's invasion of Ukraine in 2022. Since then, the EU and other G7 countries have debated how and whether to use the funds to help Ukraine.

U.S. Treasury Secretary Janet Yellen is pushing fellow G7 nations this week to agree a plan to use the profits as collateral to back a larger loan to help Ukraine.

— Reuters

Kremlin says Zelenskyy is asking for more Western help because he knows army is in trouble

The Kremlin said Tuesday that Ukrainian President Volodymyr Zelenskyy's latest appeal for more Western aid and involvement in the conflict is due to Ukraine's "extremely unfavorable" situation on the battlefield.

"Various representatives of the Kyiv regime and Zelenskyy himself have been making many statements in recent days, sometimes actually slipping into hysterics. This is due to the extremely unfavorable position of the forces of the Kyiv regime at the fronts," Kremlin Press Secretary Dmitry Peskov said, in comments translated by NBC News.

"This is also due to the quite difficult situation in which the Ukrainian military finds itself, despite all the promised help. The] [supplies- are not as regular as hoped for. And most importantly, there is a growing understanding that even if this rhythm of military supplies is restored, this will still not allow the Ukrainian Armed Forces to change the dynamics at the fronts. This understanding is growing and it does not add confidence or balanced judgment to the Kiev regime representatives," he added.

Peskov's comments come after Zelenskyy told Reuters Monday that he was trying to get Ukraine's partners more directly involved, asking them to help intercept Russian missiles and to allow Ukraine to use Western weapons against Russian military equipment at the border and targets inside Russian territory.

He said he understood they were wary of antagonizing Russia, however. "It's a question of will," Zelenskyy told the news agency. "But everyone says a word that sounds the same in every language: everyone is scared of escalation."

Zelenskyy told Reuters that the situation on the front lines had stabilized in the last week, though he conceded that Ukraine's forces had been in a more difficult position after Russia launched a new offensive in the northeast.

— Holly Ellyatt

Finland calls on EU to help prevent 'weaponized' migration from Russia

Finland called on the European Union to help prevent what it calls "instrumentalized" or "weaponized" migration at its border with Russia.

Finland has closed its borders with Russia in recent months, accusing the country of deliberately sending undocumented asylum seekers to its border in order to try to destablize the country, a new NATO member. Moscow denies the accusation.

On Tuesday, the Finnish government submitted a proposal to parliament on a new border security law that would allow border agents to prevent migrants who are seen as "instruments of influence" from entering from Russia.

"It is the government's duty to ensure the security of the borders, Finland and Finns in all situations," Prime Minister Petteri Orpo told a news conference, in comments reported by Reuters.

"Unfortunately the EU legislation does yet not provide us with effective tools to tackle the problem. I hope our work will pave the way for European level solutions," he added.

— Holly Ellyatt

Woman killed as Russia's Belgorod region attacked with drones, official says

A woman died during a Ukrainian drone attack on the Russian border region of Belgorod, the regional governor said on Telegram.

"A moving passenger car with a driver and three passengers was attacked by a kamikaze drone. The incident occurred near the checkpoint in the village of Oktyabrsky in the Belgorod region," Vyacheslav Gladkov said Tuesday.

"As a result of the explosion, the woman died on the spot from her wounds," he said, adding that the other passengers in the car were also injured.

Belgorod, across the border from Ukraine's Kharkiv region where a new Russian offensive is focused, has come under frequent fire from Ukrainian forces. Kyiv has not commented on this latest attack and CNBC was unable to verify Gladkov's claims.

The governor said other villages in Belgorod had come under Ukrainian fire and that agricultural enterprises in the villages of Novaya Tavolzhanka and Voznesenovka had been damaged. There were no casualties.

— Holly Ellyatt

Russia experiencing labor shortages as war demands manpower

Russia is currently experiencing a labor shortage in no small part due to the war in Ukraine, with some sectors experiencing significant problems recruiting workers, the British Ministry of Defense said Tuesday, noting that the situation could lead to a "mobilisation of labour."

Russia had a shortage of 4.8 million workers in 2023, according to estimates by the Russian media outlet Izvestia, cited by the defense ministry. The newspaper noted that the Russian transport and logistics industry was unable to fill 25% of its truck driver vacancies during 2023.

"The labour shortage has at least in part been caused by Russia's war in Ukraine, which has led to mobilisation of parts of the working population and emigration by some skilled professionals seeking to avoid the call-up," the defense ministry said in an intelligence update on X on Monday.

More recently, the labor shortage has been exacerbated by restrictions on migrant employment implemented following the March 22 terrorist incident in Moscow, an attack claimed by an Islamic State militant group affiliate.

"As a result of the labour shortages, a group of Russian parliamentarians are looking at possible amendments to the Russian labour code. If enacted, it would mean that excess labour force could be moved under state supervision to a place of work which lacks sufficient labour. The moves will be temporary and workers will only be transferred with their consent," the U.K. said.

"However, although not coercive, it is a potential move towards the mobilisation of labour," it added.

— Holly Ellyatt

Poland arrests nine on charges of Russian-ordered sabotage

Poland has arrested nine people in connection with acts of sabotage committed in the country on the orders of Russian services, Prime Minister Donald Tusk said late on Monday.

Warsaw says its position as a hub for supplies to Ukraine has made it a key target for Russian intelligence services, and accuses Moscow of trying to destabilize the country.

"We currently have nine suspects arrested and charged with engaging in acts of sabotage in Poland directly on behalf of the Russian services," Tusk told private broadcaster TVN24.

"This includes beatings, arson and attempted arson."

He said Poland was collaborating with its allies on the issue and that the plots also affected Lithuania, Latvia and possibly also Sweden.

Tusk said earlier this month Poland would allocate an additional 100 million zlotys ($25.53 million) to its intelligence services due to the threat from Russia.

In April, two people were detained in Poland on suspicion of attacking Leonid Volkov, an exiled top aide to late Russian opposition leader Alexei Navalny.

— Reuters

Ukraine 'holding back' Russian troops near Bilohorivka

Ukraine said Monday that its military is "holding back" Russian troops near Bilohorivka, a rural settlement in the east of the country, which Moscow claimed earlier in the day to have seized.

"The defence forces for quite a long time today have been holding back the onslaught of the enemy, which is trying to somehow move forward in the area of Bilohorivka," Kyiv's general staff said in a Google-translated Facebook post.

— Karen Gilchrist

Russia's Putin speaks to Iran's interim president, Kremlin says

Russian President Vladimir Putin on Monday spoke to Iran's interim President, Mohammed Mokhber, who was previously the country's vice president, the Kremlin said in a statement.

"Both sides will emphasize their mutual desire to further consistently strengthen comprehensive Russian-Iranian interaction for the benefit of the peoples of the two countries," the Kremlin said, according to a Google-translation.

Earlier on Monday, Russian state news agency Ria Novosti had reported that Russian Deputy Foreign Minister Sergei Ryabkov said he expected all agreements previously made between the two countries to be fulfilled even after the death of Iran's president and foreign minister. The two died in a helicopter crash on Sunday.

— Sophie Kiderlin

China's foreign minister calls for close cooperation with Russia

China and Russia should stabilize the foundation of their cooperation, said China's Foreign Minister Wang Yi after meeting on Monday with his counterpart, Russian Foreign Minister Sergei Lavrov.

Wang called on both countries to maintain the security and stability of neighboring areas, according to Reuters. The minister spoke at the meeting with his counterpart in Kazakhstan's capital, Astana.

The ministers also discussed the situation in the Middle East, Ukraine and the Korean peninsula, Reuters reported.

- April Roach

Ukraine still controls over half of embattled Vovchansk, regional official says

Ukraine still holds around 60% of the embattled town Vovchansk in the Kharkiv region, Deputy Governor Roman Semenukha told Ukrainian national television on Monday, Reuters reported.

"The enemy continues to try, especially inside Vovchansk, to push the Ukrainian Armed Forces out of the town," he said, noting that assaults from Russia are not stopping.

CNBC could not independently verify developments on the ground.

Vovchansk has become a fighting hot spot and heavily contested town in recent weeks since Russia launched a fresh offensive on the Kharkiv region in the northeast of Ukraine. Russia and Ukraine have at times given conflicting information about the the situation on the ground, including on territorial gains and losses.

— Sophie Kiderlin

Russia takes control of another Ukrainian settlement, destroys drones over Belgorod, its defense ministry says

The Russian Defense Ministry on Monday said it took control of another Ukrainian settlement, Bilohorivka in the Luhansk region, according to a Google-translated post on Telegram.

That was a result of "hostile activities" and allows Russia to take on more advantageous positions, the ministry said.

Separately, the ministry said attacks from Ukraine on the border region Belgorod were thwarted. Two drones and a rocket were destroyed by Russian air defense systems, the ministry said in another Google-translated Telegram post.

Belgorod is a key region for Ukrainian attacks and at least 13 people were injured in the area after strikes on Sunday.

CNBC could not independently verify battleground reports.

— Sophie Kiderlin

Read CNBC's previous live coverage here:

Putin says Iran's Raisi was 'true friend of Russia', Ukraine and Russia exchange tit-for-tat strikes