The head of private Russian military group Wagner has defended a brutal video apparently showing the death of a mercenary who defected to Ukraine.
Putin ally Yevgeny Prigozhin said unverified footage of Yevgeny Nuzhin, 55, being struck with a sledgehammer was "a dog's death for a dog".
The convicted murderer announced in September he had changed sides.
In the video he says he was hit on the head while walking in the Ukrainian capital Kyiv and woke up in a cellar.
However, he had been held as a prisoner of war by Ukraine and it is not clear how he was free to walk around Kyiv.
Warning: This article contains distressing details
The footage of the summary killing was posted over the weekend on the Wagner-affiliated Telegram channel Grey Zone.
It begins with Nuzhin describing how he went to the front as a member of Wagner, after being recruited in August. He said he intended to change sides and "fight against the Russians", and was later captured by the Ukrainians.
After being attacked in Kyiv on 11 November, he lost consciousness and woke up in the cellar where the film was being made.
After that an unidentified man appears to attack Nuzhin with a sledgehammer. He falls to the ground and is further beaten to death.
Mr Prigozhin said in a statement that Nuzhin had "betrayed his people, betrayed his comrades".
He sarcastically described the video as "excellent directorial work that's watchable in one sitting".
"I think this movie is called A Dog's Death for a Dog," he added.
Meanwhile the Kremlin has tried to distance itself from the video, with spokesman Dmitry Peskov saying "it was not our business".
In September, after his capture by Ukraine, Nuzhin gave details of his surrender in an interview with a Ukrainian journalist.
He said he had been recruited personally by Mr Prigozhin but went into the conflict in Ukraine with the intention of giving himself up.
He was hired with the promise of a full pardon, a salary, and compensation for his family if he was killed. The reason given for recruitment was that "the Motherland is in danger".
In August the group recruited from his prison arrived in occupied Luhansk region where they were formed into assault squads.
He described their role as "cannon fodder" and said any failure to follow orders would mean summary execution.
He was then assigned to recover corpses of dead soldiers. It was during one such operation that he was able to escape and surrender.
Mr Prigozhin is a former restaurateur and close associate of Russian President Vladimir Putin.
He set up the Wagner group, a mercenary recruiting company, in 2014 – but only publicly acknowledged this fact in September.
The group first emerged in eastern Ukraine in 2014, at the start of the conflict between Ukrainian forces and Russian proxies in the Donbas, and has since been involved in fighting in Syria and several African countries.
Since the invasion in February, several of its members have been accused by Ukraine of committing war crimes.
In September Mr Prigozhin was seen recruiting convicts for Wagner at a Russian prison.
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