Russia's security services shot dead four inmates on Friday who had taken hostages at a penal colony, fatally stabbed four of its staff and posted online videos describing themselves as ISIS militants, officials said.
"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. The hostages have been released," state news agency RIA quoted the National Guard as saying.
The federal prisons service said all four attackers had been "liquidated". It said four of its staff had died of stab wounds, and others had been treated in hospital. A total of eight prison employees and four convicts had been held hostage, it said.
In one of the videos posted by the attackers, the victims were seen lying in pools of blood, one of them with his throat slashed. One of the prisoners shouted that they were ISIS.
Other videos showed the attackers pacing about in a prison yard where one of their hostages was slumped in a sitting position, his face covered in blood.
The operation to free the captives took place after President Vladimir Putin, addressing a weekly meeting of his Security Council, said he wanted to hear from the interior minister, FSB security chief and head of the National Guard about the incident.
Russia, whose defense and security agencies are heavily focused on its war in Ukraine, has seen a recent upsurge in militant attacks.
In June, a bloody ISIS-linked prison uprising took place in the southern region of Rostov, where special forces shot dead six inmates who had taken hostages.
Later that month, at least 20 people were killed in shooting attacks on a church, a synagogue and a police checkpoint in Dagestan, a mainly Muslim region of southern Russia.
In March, ISIS claimed responsibility for an attack in which gunmen raided the Crocus City concert hall near Moscow, sprayed the audience with automatic weapons fire and set the building ablaze, killing more than 140 people.
