Inmates at a Russian prison have taken several hostages, the national prison service reported on Friday.
The incident occurred during a visit by a disciplinary commission to the facility in Volgograd Region, in the south of Russia, the report said.
Governor Andrey Bocharov has confirmed that four prison employees were hospitalized following the attack. Regional medics are on standby to respond to further casualties, including by airlifting patients, if necessary, the official said.
An operation to rescue the hostages is being prepared, officials said. Three or four inmates appear to be holding them, according to media reports.
The prison is located near the town of Surovikino, some 850km south of Moscow. It accommodates male convicts and has a capacity of over 1,200.
Unverified media reports claim that one of the hostage-takers had been convicted of terrorism offenses, and that he and his group had declared allegiance to Islamic State (IS, formerly ISIS).
In their communications, the criminals reportedly described their riot as revenge for “our brothers” – other IS supporters held in Russian custody. The news outlet claimed that they specifically named the perpetrators of the massacre at Crocus City Hall in March.
There may be as many as three fatalities, according to the reports, which cited footage purportedly recorded inside the prison. This appears to show a man in prison clothes armed with a knife, and motionless bodies in guard uniforms lying on a blood-covered floor.
A prison warden is understood to be receiving treatment in an intensive care unit after being seriously injured during the altercation.
The perpetrators have reportedly demanded a ransom of $2 million in cash and a helicopter to escape the facility in exchange for the remaining hostages’ lives.
Last month, a hostage crisis involving self-proclaimed IS supporters unfolded at a prison in the southern Russian city of Rostov-on-Don. The perpetrators were killed by special forces during a rescue operation.