 Complete the following phrase:  In early 2009, the leader of pan-Caucasian mujahideen, Dokka Umarov, announced the revival of the group as Riyad-us-Saliheen Brigade of Martyrs without its Chechen part of the name, although the group is often referred by media as such anyway, saying he has 20 people fully prepared for martyr operations. Since then the now much more ethnically-diversified group took responsibility for a series of suicide and other attacks in the Russian republics in North Caucasus and elsewhere, including the 2009 car bombing which killed at least 25 at police headquarters in Nazran, Ingushetia, a car bomb assassination attempt at the Ingush president Yunus-Bek Yevkurov, and the killing of scores of policemen in numerous smaller suicide attacks in Chechnya and Ingushetia, and since the beginning of 2010 eventually also in Dagestan. It also took responsibility for the 2009 Sayano-Shushenskaya hydro accident, was blamed by some for the 2010 Moscow Metro bombings, and has also been alleged to be behind the 2011 