Officers had been gathering for a meeting when the bomber struck
A suicide bomb attack in Russia's restive North Caucasus republic of Dagestan has killed six policemen and wounded 14 more, officials say.
The attacker tried to drive a car loaded with up to 70kg of explosives into a traffic police station as officers were gathering, police say.
But his bomb was detonated when the car was rammed by a police jeep.
The death of the officers involved prevented an even worse tragedy, said the local police chief.
"The police spotted the suspicious car and rammed it from the side after which the explosion took place," a police spokesman was quoted as saying by Reuters news agency.
The blast, which happened at around 0800 (0500 GMT), shattered windows more than 200m away.
Wednesday morning's attack in Dagestan's capital Makhachkala was similar to a bombing in nearby Ingushetia last August that left 24 people dead, says the BBC's Richard Galpin in Moscow.
Footage showed the bomber's vehicle (right) moments before the explosion
The predominantly Muslim region has seen an increase in attacks by Islamist insurgents over the past year.
Russian forces have fought two wars against separatists in the mainly Muslim republic of Chechnya since 1994. The conflicts claimed more than 100,000 lives and left the region in ruins.
Chechnya has in recent years been more peaceful, but the fighting has spread to Dagestan and Ingushetia, where correspondents say a violent Islamist insurgency is growing.
Poverty, unemployment and the brutal tactics of the security forces are reckoned to be some of the main factors driving young men into the ranks of Islamist rebel groups, which want to drive the Russians out of the region, says our correspondent.