Russian anti-terror officials say they have identified the two suicide bombers who killed 34 people in the city of Volgograd in December, and detained two alleged accomplices.
The announcement came as international fears grow about security surrounding the Sochi Winter Olympics.
The Russian officials would not confirm if the two were the same men who posted a video earlier this month claiming responsibility for the blasts and threatening another attack on the Sochi Games, which open on Feb. 7.