MAKHACHKALA, Russia A suicide bomber killed at least six policemen and wounded another 14 people on Wednesday in Russia's southern region of Dagestan by detonating a car packed with explosives at a traffic police depot.
Russia is fighting an escalating Islamist insurgency in the North Caucasus and President Dmitry Medvedev says the upsurge of violence over recent months is the country's single biggest domestic problem.
The suicide bomber tried to drive a Neva car packed with explosives into a traffic police depot at 0755 (0455 GMT) on the outskirts of Dagestan's capital, Makhachkala, but was rammed by a police UAZ jeep before exploding, a police spokesman said.
"The police spotted the suspicious car and rammed it from the side after which the explosion took place," the police spokesman said, adding that the policemen who rammed the car were killed in the resulting explosion.
Windows were blown out over 200 meters (650 ft) away by blast, which bomb experts from Russia's domestic intelligence agency, the Federal Security Service, said was equivalent to about 50-60 kg (110-130 lb) of TNT.
A doctor at the local hospital told Reuters on condition of anonymity that the death toll could increase, but declined to give any further details.
The patchwork of republics along Russia's southern flank have seen a wave of attacks over the past year that leaders say are fueled by a potent mixture of clan feuds, poverty, Islamism and heavy-handed tactics by law enforcement agencies.
The growing turbulence has raised concerns that violence could spread from the mainly Muslim North Caucasus to the major cities of the Russian heartland.
Medvedev in November said poverty, endemic corruption and widespread despair were driving young men from Dagestan and Ingushetia into the hands of Islamist rebels, who say they want to turn the North Caucasus into a sharia state independent of Russia.
Critics says the Kremlin's North Caucasus policy is in tatters after years of throwing oil money at the regions while using the security services to crack down hard on militants, and warn that the situation in the region is swiftly deteriorating.
(Writing by Guy Faulconbridge, editing by Matthew Jones)