Moscow (CNN) -- Two policemen were killed by a suicide car bomber in Russia's North Caucasus republic of Dagestan, the Dagestani Interior Ministry said on its website Monday.
The ministry said the officers were patrolling the town of Kizilyurt in a minivan around midnight when an unidentified bomber sitting in a parked Lada car set off an unidentified explosive device in his car as the police minivan was passing by.
The explosion left a crater 1.5 meters (5 feet) wide and 15 centimeters (6 inches) deep, the ministry said. The police minivan was burned out, the ministry said.
Dagestan has been hit by a series of deadly attacks recently, including fatal bombings and shootings.
It is the largest and most volatile of the five Northern Caucasus regions. Rebels continue to stage frequent attacks on security forces, police and civilians.
In August, the head of the Federal Security Service Alexandr Bortnikov told the Russian president that in the first six months of this year, 169 terrorist acts were committed, of which 110 took place in Dagestan.
In recent years, Dagestan has faced ethnic friction, spillover from the discord in neighboring Chechnya and attacks on government officials by militant Islamists, the International Crisis Group has said.