At least 12 police officers suffered injuries when unknown assailants attacked a police convoy in Russia's North Caucasus republic of Dagestan on Saturday, local media reported.
The convoy was escorting a riot police (OMON) squad to carry out tasks in the mountainous part of the republic, said a source in the regional Interior Ministry, Xinhua reported.
Around noon Moscow time (0800 GMT), at Gubden village in the Karabudakhkent district, an explosive device went off on the route of the convoy, followed by firings from automatic weapons.
"The exchange of fire went on for about two hours. Twelve OMON fighters received injuries," the source told Russian news agencies.
An unnamed spokesman for the Interior Ministry also confirmed the attack, saying "the number of those injured and the circumstances of the incident are being clarified."
Also on Saturday, a major terrorist act was foiled in the republic as police defused an improvised explosive device at Novosulak village in the Kizilyurt district near the entrance to a food store.
On July 23, Dagestani authorities issued an ultimatum to the militants demanding they stop terrorist attacks.
Violence is common in Russia's North Caucasus republics, especially Chechnya, Dagestan and Ingushetia, with militants frequently targeting police and officials.
Moscow has vowed to tackle the problems of unemployment, clan rivalry and corruption, which are viewed as the main reasons for violence in the region.