MOSCOW — The Chechen warlord Doku Umarov, who claimed responsibility for a string of Russian terrorist attacks in the name of Islam, has died, according to a website sympathetic to Islamist militants fighting against Russian rule in the North Caucasus.
"The Commanders of the Caucuses Emirate officially inform of the shakhid of Caucus Emirate Emir Doku Umarov," the Kavkaz Center website reported. Shakhid means one who died for faith.
NBC News was unable to independently confirm the claim and there have been previous reports of Umarov's demise.
Umarov rose through the ranks of the Chechen independence movement after joining the insurgency against the Russian Federation in 1994 and fighting in a second war that began in 1999.
In 2007, he split off from some of his old political allies and announced a new religion-based mission with the aim of uniting Dagestan and Chechnya into a single Islamic state ruled by Sharia law.
Groups affiliated with his separatists went on to say they had orchestrated a string of attacks over the years including a blast that derailed the high-speed Nevsky Express train between Moscow and St. Petersburg, killing 27 people.
That was followed by the March 2010 suicide bombings of the Moscow subway, in which 39 people died. Umarov said the attack was retribution for the death of four garlic-picking villagers at the hands of security forces.
Umarov also claimed he ordered the suicide bombing at Moscow's Domodedovo International Airport, which killed 36 people in February 2011.
Shortly before the 2014 Winter Olympics, he called on militants to "do everything possible" to prevent the upcoming Winter Olympics in the Russian city of Sochi. The games went ahead without incident.
The video of that address also appeared on the Kavkaz Center website.
Henry Austin reported from London.