Two Russian police officers have been injured after an unidentified gunman opened fire on them and then hurled a grenade in the North Caucasus republic of Karachayevo - Cherkessia.On Monday night, a police patrol of two officers stopped a man to check his documents in the suburbs of the city of Cherkessk, situated 1,320 kilometers(820 miles) south of Moscow, the RIA Novosti news agency reported. “Policemen noticed a man carrying a bag and hiding his face. One of the policemen asked for his documents, but the suspect attempted to flee and having opened fire wounded one of the officers, ” a spokesman for the Russian Interior Ministry said. Another policeman opened fire in return and the armed man threw a grenade at him. The second policeman was wounded in the blast. The suspect managed to escape and law enforcement forces have launched an operation in the area to find and arrest him. Russia has been fighting militants since the mid 1990s in its North Caucasus region, where the republics of Chechnya, Dagestan, and Ingushetia have been the scene of sporadic attacks and militant clashes. Violence first broke out in Chechnya in 1994, when 250,000 people were forced to flee to neighboring territories because of a war between Chechen separatists and the Russian Army. After a short - lived period of relative peace from 1996 to 1999, war resumed following attacks blamed on Chechen militant groups. An estimated 100,000 people have been killed and thousands more displaced in the conflict.