At least six police officers have died and another 16 wounded in Dagestan, in Russia's North Caucasus, after being targeted by a suicide car bomber.

The bomber tried to drive a Neva car packed with explosives into a traffic police depot on the outskirts of Makhachkala, the republic's capital, but was rammed by a police jeep before detonating the explosives.

"The police spotted the suspicious car and rammed it from the side after which the explosion took place," a police spokesman said, adding that the policemen who rammed the car were killed in the resulting explosion.

The incident occured as officers were lining up outside the building for roll call on Wednesday morning.

A similar bombing in a neighbouring republic in August killed 24 people and injured more than 200.

In that attack, a man succeeded in crashing a bomb-laden van through the gates of the police station in Nazran, Ingushetia.

Russia's predominantly Muslim republics in the North Caucasus have seen a sharp rise in violence in the past year, with many of the attacks targeting police and other officials.

Some describe the violence as a civil war between Kremlin-supported local governments and Islamist fighters.