GROZNY, October 26 (RIA Novosti) - Two policemen were killed when they attempted to check the documents of bus passengers in the Russian North Caucasus republic of Chechnya, a spokesman for investigators said Monday.

"The policemen had received intelligence that two members of illegal armed units were inside the bus," the spokesman said.

He said police officers stopped the bus at a checkpoint in the Naur District of Chechnya, and one of the two suspected militants opened fire, killing one officer. The other was taken to a hospital but died of his wounds. The suspects fled the scene.

An investigation is underway.

Militant attacks and clashes remain common in Russia's North Caucasus although the Kremlin campaign to fight separatists and terrorists in Chechnya has officially ended. Violence often spills over into nearby republics, in particular Ingushetia, Dagestan and Kabardino-Balkaria.