A Chechen warlord thought to be responsible for orchestrating a number of Russian terrorist attacks has died, NBC News reported. The news of Doku Umarov's death was posted to an Islamist website sympathetic to North Caucasus militants fighting Russian rule. NBC News was unable to confirm the claim and there have been reports of Umarov's death in the past. Umarov claimed he ordered suicide bombings on the Moscow subway system in March 2010, an attack that killed 39 people. A suicide bombing at Moscow's Domodedovo International Airport, also believed to be ordered by Umarov, killed 36 people in Feb. 2011.