MOSCOW: A court in Volgograd has convicted four men for their roles in the twin suicide bombings that killed 34 people in the southern Russian city a year ago and heightened security fears ahead of the 2014 Sochi Winter Olympics, investigators announced Friday. All four men are from Dagestan, a republic in Russia’s North Caucasus that is the center of insurgency.

Alautdin Dadayev and Ibragim Magomedov were found guilty of complicity in terrorism for sheltering the two suicide bombers as they prepared the explosives they later used to blow themselves up in a train station and on a crowded electric trolleybus, the spokesman for the federal Investigative Committee said. Both men were sentenced to 19 years in prison.

Magomed and Tagir Batirov were convicted of transporting the suicide bombers to Volgograd in a heavy truck by hiding them inside a load of hay, investigative agency spokesman Vladimir Markin said in a statement. They were each sentenced to five years and 10 months.

A week after the suicide bombings of Dec. 29 and 30, security forces surrounded a group of suspected militants who had holed up in Izberbash.