A Russian defector has openly admitted to torturing Ukrainians with brutal interrogations and threats of rape in a landmark new interview.
Konstantin Yefremov, the most senior officer to speak openly, said: "I apologise to the whole Ukrainian nation" as he detailed horrors at the hands of Russian troops.
He said he witnessed men being shot and beaten at a site in the Zaporizhzhia region, in southern Ukraine.
One "crazy" colonel knocked an inmate's teeth out and shot people in their limbs.
Mr Yefremov was deployed to Ukraine last year from Chechnya, in Russia's North Caucasus.
They were sent there under the guise of taking part in "military exercises", he told BBC's Russia Editor Steve Rosenberg.
"At the time no one believed there would be war. Everyone thought this was only a drill. I'm sure even senior officers didn't know", he continued.
Once he realised it was a war he claimed he wanted nothing to do with it and attempted to flee. But he had to abort his plans after the news got back to his Commander who threatened 10 years for desertion and alerted the police.
He eventually managed to leave the army in June and then fled Russia with the help of a Russian human rights group.
When he and his troops were stationed in Melitopol, southeastern Ukraine, he witnessed interrogations and mistreatment of Ukrainian prisoners.
He recalls a day when three prisoners were brought in.
Mr Yefremov says the Ukrainian prisoner had a blindfold on.
He told the BBC: "The colonel put a pistol to the prisoner's forehead and said 'I'm going to count to three and then shoot you in the head.'
"He counted and then fired just to the side of his head, on both sides. The colonel started shouting at him. I said: 'Comrade colonel! He can't hear you, you've deafened him!'"
Another prisoner was shot in the arm and Mr Konstantin claims his men dressed him up in a Russian uniform and took him to hospital.
He said: "We told him: 'Don't say you're a Ukrainian prisoner of war, because either the doctors will refuse to treat you, or the injured Russian soldiers will hear and shoot you and we won't be able to stop them."
Mr Yefremov wanted to end his interview by apologising to Ukraine.
He said: "I apologise to the entire Ukrainian nation for coming to their home as an uninvited guest with a weapon in my hands. Thank God I didn't hurt anyone. I didn't kill anyone. Thank God I wasn't killed.
"I don't even have the moral right to ask for forgiveness from the Ukrainians. I can't forgive myself, so I can't expect them to forgive me."
