Four officers at a maximum security prison in Russia were killed after inmates who identified themselves as affiliated to ISIS took several staff hostage, Russian state media reported.

Russian special forces said the alleged hostage takers were all “eliminated” in an operation that saw some hostages freed, at the penal colony in the town of Surovikino.

The National Guard of Russia, also known as the Rosgvardia, wrote on Telegram: “Snipers from the special forces of the Russian National Guard in the Volgograd Region neutralized four prisoners who had taken prisoner employees hostage with four precise shots; the hostages were freed.”

Graphic footage circulating on social media showed three uniformed prison staff members lying motionless in pools of blood, one with his throat slashed. A fourth staff member is seen on his knees in a doorway.

In another video the apparent hostage takers can be seen waving ISIS flags.

Inmates captured the correctional facility staff at a disciplinary commission meeting, Russia’s Federal Penitentiary Service of Russia earlier told state media outlet TASS.

“At a meeting of the disciplinary commission (where cases of malicious violators are considered, among other things) of the colony, several prisoners seized employees,” the penitentiary service said, according to TASS.

Eight prison officers and four inmates were taken hostage, according to RIA Novosti.

Russian President Vladimir Putin said Friday that the head of the Federal Penitentiary Service reported to him about the situation in the Volgograd colony.

The incident follows another hostage situation in Russia in June, when two employees of a pre-trial detention center in the southern Russian city of Rostov-on-Don were rescued after being held hostage for several hours by six detainees.

The detainees had links to ISIS and were killed in the operation.

This story has been updated with additional information.