Three police were killed by a suicide bomber who detonated a bomb in a car outside a police station in Russia's Chechnya region on Monday, an national anti-terrorism body said.
Five police were also wounded in the bombing, which highlights the instability in the North Caucasus as Russia prepares to hold the Winter Olympics in nearby Sochi in February.
Russian President Vladimir Putin has called for increased security in the mainly Muslim region, where insurgents are waging an insurgency to establish an Islamist state.
A regional Interior Ministry official told Russian news agency Itar-Tass that police had tried to stop the car before it reached the police compound, near the border with Ingushetia.
Suicide bombings are rare in Chechnya, where separatists have fought two wars against Russian soldiers since the collapse of the Soviet Union in 1991 and which is now ruled by Kremlin-backed leader Ramzan Kadyrov.