Russian security forces have killed four militants and detained dozens of others in an operation in Russia’s southern region of Chechnya.

According to the region’s chief, Ramzan Kadyrov, the militants, who were members of an illegal armed group, were “annihilated during a special operation on Wednesday evening,” media reported Thursday.

He said a member of the local security personnel was also killed during the operation. The militant group, according to Kadyrov, posed a serious threat to the region.

Russian authorities say hundreds of people in the region have left to join the Takfiri Daesh terrorist group in Iraq and Syria. They now fear that their return could pose serious security threats to the country.

Russia has fought two wars against separatists in the region over the past decades. The region is now governed by Kadyrov, who was a former militant, but is now loyal to the Russian government.

The security situation in the region, however, remains volatile.

In December last year, security forces killed another 11 gunmen in Chechnya after the militants attempted to target police forces in the provincial capital, Grozny.