A video showing Chechen insurgent leader Doku Umarov was released Feb. 7, 2011, after a deadly suicide bombing at Russia's largest airport for which he claimed responsibility. Russian authorities say Chechen separatists were involved in a foiled plot targeting Sochi, the site of the 2014 Winter Olympics. (Associated Press)

A video showing Chechen insurgent leader Doku Umarov was released Feb. 7, 2011, after a deadly suicide bombing at Russia's largest airport for which he claimed responsibility. Russian authorities say Chechen separatists were involved in a foiled plot targeting Sochi, the site of the 2014 Winter Olympics. (Associated Press)