Russian Islamist leader Doku Umarov has claimed responsibility for the bomb attack on Moscow’s Domodedovo airport last month which killed 36 people. Mr Umarov heads the Caucasus Emirate, a shadowy terrorist group that dreams of creating an Islamic state in Russia’s north Caucasus region and operates mainly in the wild backcountry of Dagestan, Chechnya, and Ingushetia. Speaking in a video...