A Chechen rebel warlord who threatened to attack the Sochi Olympics is dead, Chechnya's Kremlin-backed strongman said, but he offered no proof and his claim could not be verified. Chechen leader Ramzan Kadyrov said on his Instagram account on Thursday that Doku Umarov, who urged his fighters to strike the Games, had died, a claim he has made repeatedly in the past. The information about Umarov's death came from intercepted communications between other rebel leaders who were discussing his replacement, he said, but he did not make clear when the conversation took place or how it was heard. The insurgents were too busy trying to find a replacement to Umarov to pose any threat to the Olympics that start February 7, Kadyrov said. "That's why all the talks about the threat to Sochi are absolutely groundless." The Interfax news agency quoted an unidentified source in a Russian security agency as saying they could not confirm Umarov's death. Interfax also quoted Kadyrov as saying that Umarov's body had not been found but that his forces were looking for it. Umarov is the leader of the so-called Caucasus Emirate, a loose alliance of rebel groups seeking to create an independent Islamic state in Russia's North Caucasus. He has claimed responsibility for numerous terror attacks in Russia.