Russian investigators said Monday they had detained six prison guards over a video showing officers brutally beating an inmate which was leaked to an independent newspaper.
The group of prison service employees, "acting deliberately, clearly exceeding their official powers, used violence against a prisoner," investigators said.
Human rights activists regularly report torture, humiliation and beatings in Russian prisons, but the leak of such an explicit video is rare.
The branch of the Investigative Committee for the Volga city of Yaroslavl, where the video was shot at a penal colony, said "today six people have already been detained."
"The criminals delivered multiple blows with hands, feet and unidentified objects to the man's torso and limbs," it said in a statement.
The 10-minute video posted by the Novaya Gazeta newspaper on Friday shows a group of 18 uniformed men methodically beating a man who is pinned down on a table as he groans and pleads for mercy. They also pour water on his head.
The prisoner, named as Yevgeny Makarov, was left covered with bruises and cuts on his legs which were swollen and infected, his lawyer wrote in a report quoted in the newspaper.
Makarov said he lost consciousness several times.
The video clearly shows the men's faces. Novaya Gazeta reported that it was shot in June 2017 but criminal action was only launched after the publication of the video.
Investigators said they had identified all those involved and were going through legal procedures to detain the rest of the participants.
They said that they would also look at the actions of the prison governor and top regional prison officials.
The video was shot with a portable video recorder that according to the law prison officers are obliged to carry.
The prisoner is still in jail but has been visited by a rights ombudsman and is relatively safe in a one-man cell, his lawyer Irina Biryukova told the Russian channel TV Rain.
Threats from guards
Rights group Public Verdict, which passed the video to Novaya Gazeta, said Monday that Biryukova has fled Russia after receiving threats and had asked for state protection for family members.
Biryukova told TV Rain that a reliable source in the region had informed her that prison guards had voiced personal threats against her.
"For my safety, we decided that it was necessary for me to leave Russia for the meantime," she said.
Amnesty International called on Russian authorities to "act immediately" to protect the lawyer.
"The launch of the investigation into the allegations of torture is a welcome first step towards justice," the rights group said in a statement.
"However, in the absence of a national mechanism which systematically works to prevent torture, the criminal case against Makarov's torturers will be an exception to the rule."
Biryukova said she was hopeful that the publicity around the case would lead to more arrests and eventual sentences, and that she would return to Russia soon.
The regional Investigative Committee told TASS state news agency it was checking into threats against Biryukova and could launch criminal action.
The case is not the first allegation of brutality against prisoners to emerge from the Yaroslavl colony.
Last year, Novaya Gazeta reported an inmate who was sentenced for taking part in protests against the return of Vladimir Putin to the Kremlin in 2012 was tortured there in a punishment cell.