The death of Chechen warlord Doku Umarov 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.