Two people are dead following another explosion in the southern Russian city of Vladikavkaz, near Chechnya.
It is the second deadly blast in three days to strike the capital of North Ossetia, a Russian republic near war-torn Chechnya.
The North Ossetian department of Russia's Federal Security Service says first reports indicate the explosion was caused by a grenade placed near a house.
No group has claimed responsibility.
Federal and regional authorities are already investigating the cause of another blast on Tuesday near the central market and a bank in Vladikavkaz. Two people were killed in that incident and 10 others injured.
Because of the republic's proximity to Chechnya, separatists are often among the first people suspected by Russian officials. But Interior ministry investigators say the blasts could be the work of rival criminal gangs.