A British fighter held by pro-Russians was evidently forced to read a humiliating confession on video the day after captives were threatened with the death penalty.
Andrew Hill, from Plymouth, was filmed admitting to "unwittingly" being involved in "war crimes" and pleading for leniency.
The 35-year-old is apparently being held in Donetsk in eastern Ukraine, which Russians forces occupied early in their offensive.
In the footage bearded Mr Hill, a father of four, can be seen seemingly reading a statement and occasionally stumbling over his words.
The Mirror is not publishing the video.
“After coming to Ukraine I realised it was hell here," he says, before adding that the foreign mercenaries he was fighting with until last week were "really bad people and sadists".
"They were ready to do any dirty job needed for money," Mr Hill said.
"They don't come to war for money, they do get money, but they do it because they enjoy it. Many of them do not understand the Ukrainian and Russian language."
Mr Hill is filmed saying that the mercenaries' lack of understanding of the language is why “they shoot (civilians), kill them and injure them indiscriminately."
He adds: “They stole valuable things from these people without any shame at all. Mercenaries also tortured Russian soldiers and Russian fight activists.
“They cut off their fingers and they torture them. Prisoners were severely beaten and they were deprived of food and a drink.
“I've never seen such cruelty on this scale before."
The script Mr Hill appears to have been given hits on key talking points pushed repeatedly by the Russian propaganda machine.
“Supporters of the Neo-Nazi and the nationalist ideology prevail in this camp,” Mr Hill continues.
“They are proud of the tattoos of the swastikas and the double-S's emblems. It was awful.
“Unfortunately I found myself among these terrible people and unwittingly became involved in these war crimes.
“I understand everything has been done wrong and I hope for leniency from the Donetsk People Republic.”
In the UK his partner Candice Morgan has been making frantic efforts to get him back to the UK, spreading the word that her partner is a "prisoner of war."
She and his family “are trying everything in our power and are in contact with the right people to try and get him home safely”.
"This isn’t an easy process and will take time," Candice said.
"Again, I know how hard it is not knowing what is happening but please can everyone be reassured that this situation has not been taken lightly."
On Friday, when Mr Hill was first seen on Russian TV, it was reported that he had been held in Mykolaiv region after the group he had been fighting with was defeated and he was injured.
In that appearance his head was bandaged and his arm was in a sling.
Just a week before his capture he made an impassioned plea to his Facebook followers for more resources to fight the Russians.
On Monday, the DPR’s state prosecutor Andrei Spivak threatened to execute two other British captives Shaun Pinner, 48, and Aiden Aslin, 28.
He said this was the maximum punishment for the crimes with which they were charged in the unofficial republic, which includes the murder of civilians .
Pinner appeared detained and mumbled a reply to the charges.
Aslin said: "I understand fully what I am accused offend I agree with it fully up to the part about murdering civilians - I don’t agree with (this)."
