Gunmen opened fire on two Orthodox temples, two synagogues, and a police station in Derbent and Makhachkala on Sunday during the Orthodox festival of Pentecost.

Several civilians were reportedly also killed, including 66-year-old Father Nikolai Kotelnikov, who had served more than 40 years in Derbent.

According to reports, the attackers slit his throat.

Footage posted on social media shows people wearing dark clothes shooting at police cars before a convoy of emergency service vehicles arrives at the scene.

Six of the unidentified attackers, who are thought to belong to the Islamic State, are dead, and police are hunting for others.

Following the attack, the Islamic State published a statement praising the “brothers from the Caucasus.”

According to the American Institute for the Study of War (ISW), the reference to the Caucasus suggests that the attack was carried out by the so-called Caucasian Vilayet, a branch of the Islamic State in the north Caucasus.

The attacks come just three months after Islamic State gunmen opened fire at a rock concert in the Crocus City Hall on the outskirts of Moscow, which left over 140 dead.

Since then, the ISW has said that Russian authorities have been attempting to crack down on “the growing influence of the Islamic State and the Caucasus Vilayet.”

The institute added that “Russia's increasingly tense relations with Muslim minorities, especially in the Caucasus, will likely continue to provide the Caucasus Vilayet and other regional extremist groups with a valuable recruitment base.”