Special forces snipers shot dead all four of the prisoners who had staged an attack using knives, stabbing dead four prison officers and taking eight others hostage as well as four fellow inmates.

"Snipers of the special forces of the Russian National Guard in the Volgograd region, with four precise shots, neutralized four prisoners who had taken prison employees hostage," state news agency RIA quoted the National Guard as saying. "The hostages have been released,"

Video footage filmed by the attackers showed prison officers lying motionless and bloodied on the ground, the Reuters news agency reported on Friday.

In one of the videos, an attacker shouts that they are mujahideen of Islamic State, Reuters said.

Reuters said one of the attackers appeared to be wearing an improvised explosive vest while others wielded knives and hammers.

Poland’s national press agency said the attackers had demanded a helicopter and $12 million, citing Russia’s Shot channel

Russian media said the suspects were from Uzbekistan and Tajikistan and that three of them were serving drug-related sentences while the other was doing time for unpremeditated murder.

The event is the second of its type to have occurred in Russia since June and took place on Friday at the high-security IK-19 penal colony in the town of Surovikino, about 850km south of Moscow. The facility is designated as a “harsh regime” and has a capacity of over 1,200 inmates, Al Jazeera said.