Islamic extremist groups based in the nearby Caucasus mountains have vowed to disrupt the Olympics .
Islamic extremist groups based in the nearby Caucasus mountains claimed responsibility for twin December suicide bombing in Volvograd -- roughly 500 miles away -- that left more than 30 dead .
Islamic extremist groups based in the nearby Caucasus mountains have vowed to disrupt the Olympics and claimed responsibility for twin December suicide bombing in Volvograd -- roughly 500 miles away -- that left more than 30 dead .