A suicide bomber was responsible for at least one of two blasts in a town in Russia's volatile North Caucasus region of Dagestan, where 12 people have been killed, investigators say.
Among the dead in the Dagestani town of Kizlyar were nine police officers and one investigator.
"Twelve people were killed, nine of them police," the investigative committee of Russian prosecutors said in a statement. Another 23 people were wounded.
The blast came two days after female suicide bombers killed 39 in attacks on the Moscow metro which the authorities have linked to militants from the North Caucasus.
Russia's investigative committee said that the first blast was set off as a police car drove out of the local interior ministry building.
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Just 20 minutes later, a suicide bomber dressed in police uniform blew himself up as investigators and police were probing the scene of the first blast, the statement said.
The Interfax news agency said one of victims was the head of police in the area, Vitaly Vedernikov.
"According to preliminary information, there were twin blasts" in the Dagestani town of Kizlyar, the spokesman said.
An insurgency against Russian rule has taken hold in Dagestan in recent years, with many fighters reportedly spilling over from Chechnya.
In January of this year, a suciide bomber attempted to blow up a police station in Mackhachkala, killing at least six officers.
