A suicide bomber set off a powerful car bomb outside a police headquarters in the restive Russian republic of Dagestan, killing seven police and wounding 15, officials said.
The 8am explosion occurred in front of the traffic police headquarters in Makhachkala, the Dagestan capital, investigators said in a statement, calling the perpetrator a "suicide bomber".
The bomber's car was stopped by guards at the entrance into the police headquarters and a police car drove out to meet it, they said, praising the policemen for their "vigilance and selflessness".
"Realising that he wouldn't be able to get into the headquarters, the suicide bomber triggered an explosive device," the Investigative Committee said.
Investigators put the initial death toll at six, but one victim later died in hospital, NTV television reported, quoting the chief doctor at the Republican Orthopaedic and Trauma Centre, Magomed Omarov.
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A further 15 were hospitalised and some underwent surgery, Omarov said.
Television footage showed a deep crater outside the police headquarters, roofs blown off neighbouring buildings and piles of bricks lying on the ground. Cars parked on the street were crumpled by the blast.
The unidentified suicide bomber, who drove the car alone, was a young man in dark clothing, according to witnesses, the deputy head of public security police in Dagestan's interior ministry, Magomed Isayev, told NTV television.
Concerns have mounted over increased militant attacks throughout Russia's Caucasus region, where Islamist militants have been battling pro-Kremlin local authorities and Russian security forces in a sporadic insurgency.
