A suicide bombing in Chechnya has killed four people and injured three others in the latest violence in the Russian region.
Two officers and a soldier died in the explosion on Monday when their armoured vehicle travelling between the garrison town of Khankala and the capital, Grozny, made a stop, Vasily Panchenkov, a spokesman for the interior ministry troops, said.
"They got out of the vehicle. A blast took place," he said, adding that a civilian was also killed.
Three more troops received serious injuries and were admitted to hospital, Panchenkov said.
He said the blast was detonated by a bomber with a suicide belt, adding that body fragments believed to belong to the attacker were found at the scene.
A Reuters witness saw the remains of three people in camouflage clothing lying at the roadside after the blast.
Local law-enforcement officials said the blast could have been carried out by two suicide bombers. Residents said they heard two explosions, the second of which sent flames and smoke into the air.
Suicide blast suspected
Moscow-based investigators said two suicide bombers were involved.
They said the blasts occurred near the entrance to a store on the outskirts of Grozny.
In separate statements, the Chechen interior ministry and Moscow-based investigators said, however, there were two suicide bombers.
"Measures are being taken to identify terrorists and find their possible accomplices," the regional interior ministry said.
"The situation in the city remains calm. All organisations, offices, shops, markets and public transport continue to operate," it said.
The Kremlin fought two post-Soviet wars against separatists in Chechnya and the violence has since spread into the nearby regions of Dagestan, Ingushetia and Kabardino-Balkaria.
Russia in 2009 formally ended a decade-long "counterterror" operation in Chechnya, citing the return of relative stability to the mainly Muslim region.
But attacks on government officials and police including by suicide bombers remain frequent in Chechnya and elsewhere in the North Caucasus.
Critics say the continuing violence exposes the hollowness of the Kremlin's claims to have imposed control and stability in the region under the iron-fisted rule of Ramzan Kadyrov.
A former separatist fighter, Kadyrov, 35, took power in Chechnya after his father, Akhmat Kadyrov, was killed in a bomb attack as he attended a Victory Day concert in 2004.
Human rights activists accuse Kadyrov of presiding over a personal militia that carries out rampant rights abuses, torture and even murder.
Last October Chechnya celebrated Kadyrov's 35th birthday with elaborate festivities attended by Hollywood actors Jean-Claude Van Damme, Kevin Costner and Hilary Swank.