A suicide car bomb attack in the volatile Russian Caucasus region of Dagestan killed three police officers and wounded six other people on Thursday, the local interior ministry said.
The attacker blew up his car at a checkpoint at Khassaviurt, in northern Dagestan, a statement said.
It said the blast left a crater that was two metres in diameter (two yards) and 1.5 metres deep.
The North Caucasus, the southwest Russian region where Dagestan is located, witnesses near-daily violence that officials blame on militants seeking to establish an Islamic state across the impoverished territory.
Dagestan is currently the most unstable region in the Northern Caucasus, with rebels staging attacks against the pro-Kremlin local authorities almost every day.