At least three people were killed and 11 injured in an explosion outside a military barracks in the Dagestan region of southern Russia. The blast happened while soldiers were conducting a search for explosives in a street outside their base in the capital, Makhachkala.
At least one soldier is reported to be among the dead.
Dagestan, which borders Chechnya, has a history of violence by both rebel groups and criminal gangs.
"The blast happened while soldiers were checking for explosives," emergency ministry spokesman Viktor Beltsov said.
A civilian who happened to be driving through the street was injured in the explosion, he added.
A search for the attackers was under way after they allegedly fled the blast scene.
Much of the violence in this ethnically diverse North Caucasus republic is thought to have spilled over from the Chechnya conflict.
In a similar attack in July, 10 people were killed and seven were injured in a bomb attack on a lorry filled with security forces near the capital.