The Islamic State group has claimed responsibility for a shooting in Russia's volatile North Caucasus region of Dagestan that killed one and injured 11, SITE Intelligence Group said Thursday. The attack occurred Tuesday night near the citadel of Derbent, reportedly Russia's oldest city.

"With the help of Allah, the warriors of the Khalifate were able to attack a group of Russian special service officers in the city of Derbent in southern Dagestan, killing one officer and injuring the others," the terrorist monitoring organization quoted ISIS as saying Wednesday, according to Agence France-Presse (AFP).

Gunmen reportedly opened fire at people standing by the ancient citadel, which was declared a Unesco World Heritage site in 2003. A law enforcement official told Interfax Wednesday that at least 65 bullet casings were recovered at the scene, AFP reported.

Russia has had heavy security presence in the largely Muslim North Caucasus region since the separatist wars that were waged in Chechnya in the 1990s. Islamist rebels in Dagestan, a restive region just east of Chechnya, have been making several efforts to join ISIS.

At least 118 people were killed in the region between January and November as a result of the conflict, AFP reported, citing the Caucasian Knot news portal, which monitors militant activities in the North Caucasus. 

The attack came as Russia continued airstrikes in Syria targeting ISIS strongholds. Moscow began targeting the Sunni-militant group in late September and intensified its attack after ISIS claimed responsibility for downing a Russian Metrojet plane in October over Egypt, resulting in the death of all 224 people on board.