MOSCOW, May 15 (RIA Novosti) - A police checkpoint has come under fire in Russia's troubled Caucasus republic of Chechnya, a source in local law enforcement agencies said.

The accident occurred at 2.00 a.m. local time on Thursday (22.00 GMT Wednesday) as a group of unknown assailants in four vehicles attacked the checkpoint, located on the federal Kavkaz highway near the village of Assinov. There are no reports of casualties.

The six police officers who were on duty at the time returned fire, forcing their attackers to flee the scene, the source told the agency. The suspected militants are believed to have come from the neighboring republic of Ingushetia.

Sporadic terrorist attacks and militant clashes remain common in Russia's North Caucasus republics, although the active phase of the Kremlin campaign against militants in Chechnya is officially over.