Doku Umarov, "Russia's Bin Laden," reported dead by militant group

Chechen Islamist militant commander Doku Umarov is seen in a video released by the KavkazCenter jihadist media portal, July 3, 2013.

MOSCOW -- An Islamic militant group in Russia's North Caucasus is reporting the death of its leader, who had threatened to attack Sochi Olympics and was one of Russia's most wanted men.

The death of Chechen warlord Doku Umarov, who has been called "Russia's bin Laden," has been reported previously, but this appears to be the first time by the organization he headed.

The Caucasus Emirate announced the "martyrdom" of Umarov in a statement posted Tuesday on the website of Kavkaz Center,

which serves as a mouthpiece for Islamic militant groups. No cause was given.

Chechnya's Kremlin-backed leader had reported Umarov's death in January, a month before the Olympics, but his claim was not verified.

The ITAR-Tass news agency quoted Chechen leader Ramzan Kadyrov saying that Tuesday's announcement showed he was right that Umarov died in a special operation.

CBS News Moscow bureau chief Svetlana Berdnikova reports that Russian security services have refused to give any comments, as of now.