Two Russian policemen died and many people were injured in a car bomb blast at a checkpoint in the North Caucasus region of Dagestan on Monday, the interior ministry said.
The blast occurred as police officers were attempting to inspect a Lada car at a checkpoint near the village of Dzhemikent on the Caspian Sea, the interior ministry's district office said in a statement.
"Two police officers died and two more were hospitalised with injuries," it said.
A source in the region's security forces was quoted by TASS news agency as saying the blast was a suicide bombing.
"There is only a piece of the head left from the suicide bomber, a foot and a hand. One of the fingers that's left will help identify him," the source said.
"The car was sold recently, its previous owner has been identified."
Head of the region Ramazan Abdulatipov said a total of 18 people were injured.
Russia's anti-terrorist committee (NAK) said the blast was caused by a device placed in a car based on two artillery shells and was equivalent to 30 kilogrammes of TNT.
"The blast happened inside a passenger car," said a NAK statement quoted by news agencies.
Dagestan has been gripped by nearly daily violence for years due to a simmering Islamist insurgency there, though it has abated during the conflict in Syria which has seen an exodus of Russians from the North Caucasus to join the insurgent fighters in the Islamic State group and Al-Qaeda affiliate Al-Nusra Front.
In December, IS claimed responsibility for a deadly shooting in Derbent, a city in Dagestan with an ancient citadel that is popular with tourists. The victim was reportedly an employee of the Russian border service.