Four suspected gunmen, including a militant leader, were killed in Russia's volatile North Caucasus republic of Dagestan on Thursday, the RIA Novosti news agency said, quoting a local police official. Militants opened fire on police when required to stop their car for a routine check in the town of Khasavyurt on Thursday night, the official said. Police returned fire and killed all the four militants, the official said, adding that one of the dead has been identified as Umalat Magomedov, also known under alias Albaro, who allegedly led the militant underground in Dagestan. Dagestan and the other mainly Muslim regions of Russia's North Caucasus have been plagued by instability and violence recently. Skirmishes between troops and militants, and attacks on police and other officials have been reported daily. 