Russian officials say five Russian servicemen have been killed in fighting with suspected militants in the restive Caucasus region of Dagestan.

The regional interior ministry said Wednesday that several other troops were injured during a sweep against militants in Dagestan's Kizlyar district. The government forces began the operation on Tuesday.

Also on Tuesday, unknown gunmen killed Gadzi Alibegov, a senior investigator dealing with extremism, near his home in the regional capital Makhachkala.

Dagestan is a predominantly Muslim region in southern Russia, plagued by violence linked to an Islamist insurgency. Separatists in neighboring Chechnya fought two major wars against the Russian government. Although the major fighting ended about a decade ago, attacks on government targets continue almost daily.