Four people have been killed in a large explosion in the city of Nazran, capital of the southern Russian republic of Ingushetia, reports say.
The blast took place as a security forces vehicle passed a government building, Interfax news agency says.
Earlier, gunmen killed three members of an ethnic Russian family.
Explosions and gunfights have become increasingly common in Ingushetia, a largely Muslim republic bordering war-torn Chechnya.
President Vladimir Putin earlier this month announced the deployment of an extra 2,500 troops in the republic.
The Nazran blast killed four policemen, Russian news agencies reported. Three died at the scene and one later in hospital.
The explosion took place at 1900 local time (1500 GMT), one official told the Itar-Tass agency.
One police officer told the Reuters news agency a Lada car packed with explosives blew up in the town centre.
On Thursday night three men - the husband and two sons of an ethnic Russian schoolteacher - were killed in an attack.
The woman, Vera Draganchuk, escaped by jumping out of a window, police said.
The attack is the second of its kind in two months.
Lyudmila Teryokhina, a Russian teacher, and her two children were shot dead in Ingushetia in July.