NALCHIK, August 7 (RIA Novosti) - Traffic police officers have killed four unknown assailants who attacked them in Nalchik, the capital of the Russian North Caucasus republic of Kabardino-Balkaria, the Interior Ministry reported Wednesday.

“People inside a Lada Priora car, stopped by police for a check early Wednesday, opened fire and injured one policeman,” a ministry spokesman said.

The four attackers were killed by return fire, he said.

The car is being examined by sappers.

One of those killed was a gang leader in Kabardino-Balkaria and Karachayevo-Cherkessia, a police spokesman told RIA Novosti.  An investigation is underway.

The Islamist insurgency, once confined largely to the republic of Chechnya, has spread across the North Caucasus in recent years. Attacks on security forces, police and civilians are reported regularly in the neighboring republics of Dagestan, Ingushetia and Kabardino-Balkaria.