A police patrol vehicle stopped a Mercedes car containing three men for a routine check in the early hours of Thursday. As officers checked the documents, one of the men suddenly pulled out a pistol and started firing at the police, injuring two, who were later taken to hospital.
Police returned fire, wounding the assailant, who was subsequently detained. Another man escaped during the shootout. The car driver denied having anything to do with the two men and claimed to be only giving them a lift.
Police have compiled and circulated an identikit sketch of the third man as part of the hunt for the offender.
The two detainees are being questioned. Their names are not being disclosed due to the ongoing investigation.
The source said one of the men was a resident of Nalchik, the capital of Russia's North Caucasus republic of Kabardino-Balkaria, and may have been a member of an organized crime group.