MAKHACHKALA/ROSTOV ON DON, October 19 (RIA Novosti) - Four suspected militants were killed, several detained and a terrorist attack prevented in Russia's volatile North Caucasus regions overnight.

Police killed three gunmen in a shootout in Dagestan's Khasavyurt region bordering Chechnya. The shooting broke out during a routine document check, when men inside the car opened fire and were killed by return fire, local police said on Monday.

No casualties were reported among the police.

Police said two assault rifles, a pistol, two hand grenades and other ammunition were found in the car.

Another suspected militant was killed in Chechnya's Achkhoi-Martan district during a police operation, and two other gunmen were arrested, a police source said.

In Ingushetia, bomb disposal experts blew up a car loaded with explosives and left near a bus stop in the center of Nazran, the republic's largest city, a local Interior Ministry spokesman said.

"The car was parked near a bus stop on Sunday evening," he said. "Field engineers cordoned off the area and destroyed the bomb by blowing up the car."

The spokesman said police were determining the type and power of the bomb, adding the explosion was heard far outside the city. An investigation has been launched.

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