ROSTOV-ON-DON, October 2 (RIA Novosti) - A police officer and three militants were killed in a special operation in the Russian North Caucasus Republic of Kabardino-Balkaria on Friday, a spokesman for Russia's top investigation body said.

"The special operation is over. Three militants were killed," the spokesman said, adding that four policemen and a civilian were also injured.

A group of assailants, armed with guns and grenades, attacked a traffic police post in the town of Prokhladny in the early hours of Friday.

During the pursuit, the car with the attackers was blocked off near a traffic police post.

The gunmen abandoned the car and barricaded themselves in a private house. Special police units had arrived at the scene and surrounded the building, which was located near a railroad. The special operation caused a delay in train traffic for several hours.

Russia's North Caucasus republics, in particular Chechnya, Dagestan and Ingushetia, have seen an upsurge of militant violence this year, with frequent attacks on police and officials.