It's also emerged that Russian authorities are hunting two more 'black widow' suspects -- a notorious type of terrorist that's emerged in Russia's clashes with Chechen separatists. There have been years of unrest linked to an Islamist insurgency in Dagestan and the North Caucasus region, and Islamist militants have vowed to strike at the Games. In a video that surfaced Sunday, two young men believed to have been suicide bombers in last month's back-to-back bombings in the Russian city of Volgograd made an ominous promise. "We've prepared a present for you and all tourists who'll come over," the video says. "If you will hold the Olympics, you'll get a present from us for the Muslim blood that's been spilled."