Russian officials say three car bombs have killed at least four people and wounded dozens of others in the volatile Dagestan region.

A spokesman for the Interior Ministry said two of the blasts occurred just after midnight Thursday near its headquarters in the city of Makhachkala. The spokesman says a Russian police officer was among those killed.

Hours earlier, a car bomb killed at least three people and wounded several others in Makhachkala.

Islamist rebels have claimed responsibility for similar bombings in Dagestan in the past. They have been fighting for an independent Islamic state in Russia's predominantly Muslim North Caucasus. The battles have continued after two Russian wars against the separatists in Chechnya.

Chechen rebels claimed reasonability for a suicide bombing at Moscow's Domodedovo airport in January that killed nearly 40 people.