A suicide bomber killed four police officers and wounded another six in Dagestan on Thursday in the latest deadly attack in the volatile North Caucasus republic.
The suicide bomber detonated explosives at a security checkpoint as police stopped his car for a routine document check on the way into the city of Khasavyurt, the Interior Ministry said in a statement.
"Police officers stopped the … car for a [routine] check. Behind the wheel was a terrorist suicide bomber," the ministry said. "When police officers walked up to the car, he detonated the explosive device."
Six officers were taken to the hospital with injuries, officials said.
Islamist insurgents launch attacks daily as part of their campaign to turn the predominantly Muslim North Caucasus into an Islamic state, and Dagestan has emerged as the epicenter of violence.
It was unclear how many people were in the car, but the Interior Ministry said the original target was likely in Khasavyurt.
Police are under orders to clamp down on insurgent violence across the North Caucasus ahead of the Sochi 2014 Olympics. Putin told security officers last year to prevent attacks on the major events Russia will host in coming years, including the 2018 World Cup.
The Investigative Committee said the explosion tore a hole almost 4 meters wide in the checkpoint building.
Television showed pictures of the twisted wreckage of the car near the security checkpoint, where police regularly check identity papers.
Human rights groups say the insurgency is driven by a volatile mix of religion, corruption and grievances against the strong-arm tactics of some local leaders against suspected militants and their families.
The suicide bombing followed a police raid on a Dagestani forest hideout that killed five militants earlier this week.