A National Anti-Terrorism Committee representative identified the bombers as Asker Samedov and Suleiman Magomedov.
The suicide bombers detonated devices at a train station and a trolleybus in Volgograd within 24 hours of each other Dec. 29 and 30, killing 34 people and injuring nearly 100 more.
Investigators arrested two men, brothers, they believe helped transport the suicide bombers to Volgograd, ITAR-Tass reported.
"As a result of investigative actions on the territory of the Republic of Dagestan, Magomednabi and Tagir Batyrov, involved in transporting suicide bombers to Volgograd, were detained, and are currently subject to relevant legal proceedings," the Anti-Terrorism Committee said.
The Batyrovs were being questioned about their involvement in the bombings, RIA Novosti reported.