Police says alleged suicide bombers from Volgograd militant group -- state news agency . two brothers , suspected accomplices , have been detained , report says . Chechen warlord Doku Umarov , leader of the Islamist group Caucasus Emirate , last summer called on his followers to do what they could to disrupt the Games . Dagestan has been trying to address security concerns before the Winter Olympics . Security fears have been heightened since Russia bombings the 19th century .
Police says alleged suicide bombers from Volgograd militant group -- state news agency . two brothers , suspected accomplices , have been detained , report says . Dagestan has been trying to address security concerns before the Winter Olympics . Security fears have been heightened since Russia bombings the 19th century .