MOSCOW — One person was killed and 10 were wounded after at least one gunman opened fire at the ancient citadel in Derbent, a historic crossroads in the southern republic of Dagestan that has been a focus of recruiting by the Islamic State, Russia’s Investigative Committee said in a statement on Wednesday.

The committee, Russia’s equivalent of the F.B.I., has opened a criminal investigation into the attack late Tuesday at the citadel, a Unesco World Heritage site with walls dating to the sixth century.

The attack was most likely carried out by one of the “die-hard gangs or the militants who managed to survive and continue taking revenge on the peace and order enjoyed by Derbent residents,” Ramazan Abdulatipov, the head of the republic, was quoted as saying by the Interfax news agency. He expressed confidence that those responsible for the attack would be caught.

The attack came after a group of people climbed up to the observation deck in the citadel around 11:30 p.m., according to the Investigative Committee. They came under fire from the nearby forest, news reports said, and one of two border guards in the group was killed, with four other people seriously wounded.