One serviceman was killed and another one wounded when unknown assailants attacked them in the Russian North Caucasus republic of Dagestan early on Wednesday, August 21 a regional police spokesman said, according to RIA Novosti.

The incident occurred in the town of Buinaksk, about 40 kilometers (25 miles) southwest of the republic’s capital Makhachkala. An investigation is underway.

Buinaksk became the site of a counterterrorism operation on Tuesday. Nine suspected militants were killed Tuesday during an armed siege at a home in the town, “including the odious leader Bammatkhan Sheikhov,” Russia’s Anti-Terrorism Committee said in a statement.

The committee said a group led by Sheikhov had been responsible for the killing of civilians and law enforcement officials, including an attack on a military base near Buinaksk in 2010.

Over the weekend, six suspected militants were killed in Dagestan, the committee reported earlier.

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.