MOSCOW : Russia’s security service confirmed Tuesday that Chechen rebel leader Doku Umarov, whose Caucasus Emirate group claimed responsibility for a string of deadly attacks, had been “neutralised” after insurgents announced his death last month.The director of the FSB security service, Alexander Bortnikov, said that “the activities of the head of the Caucasus Emirate terrorist organisation, Umarov, have been neutralised”. Bortnikov was speaking at a meeting of the National Anti-Terrorism Committee, which quoted him on its website without giving any further details. The Islamist leader was declared a martyr on militant websites last month, but the Russian authorities did not give confirmation at the time although they are usually keen to rapidly boast of “liquidating” insurgents in the turbulent North Caucasus. Interfax news agency on Tuesday quoted a source familiar with the situation as saying that Umarov is believed to have died from a serious injury he received during a security operation in 2011. The source said Umarov’s body “has still not been found”.Umarov’s organisation, which seeks to establish an Islamic state in the mountainous North Caucasus region in southern Russia, has claimed responsibility for attacks, including the 2004 Beslan school hostage crisis in which more than 330 died and the 2011 suicide bombing in Moscow’s Domodedovo airport that killed 37 people. The Russian authorities have pronounced Umarov dead several times in the past years, only for him to resurface in videos posted online calling for jihad.