The head of Russian mercenary group Wagner, Yevgeny Prigozhin, has said that around 10,000 prisoners he recruited to fight in Ukraine have been killed on the battlefield.
Last year, Prigozhin toured Russian prisons in a bid to convince inmates to fight with Wagner in Ukraine, in exchange for a promised amnesty upon their return should they survive.
Convicts are believed to have been used as cannon fodder in Ukraine, accounting for most of Wagner's losses in the pro-Western country.
"I took 50,000 prisoners of which around 20 percent were killed," Prigozhin said in a video interview published late Tuesday.
Prigozhin said a similar percentage were killed among those who had signed a contract with Wagner, but did not give a precise figure.
Both the mercenary outfit and regular Russian troops said at the weekend that the flashpoint town of Bakhmut in eastern Ukraine had fallen, but Kyiv said Ukrainian forces continued to fight for it.
Prigozhin, whose influence has risen hugely during the more than year-long offensive, has scathingly criticised Russia's top brass, accusing them of being responsible for huge losses.
He has accused Russian Defence Minister Sergei Shoigu and Chief of the General Staff Valery Gerasimov of being incompetent and causing excess losses.
"There are now tens of thousands of relatives of those who were killed. Probably there will be hundreds of thousands. We cannot hide from this," he said.
He called on Russia's military elite to send their own children to the front.
Prigozhin, a businessman close to President Vladimir Putin, has slammed the Russian elites, saying their children live comfortably while men from impoverished regions die in Ukraine.
Prigozhin said his fighters will pull out of the destroyed city by June 1 and transfer control to the Russian army.
In early May, the White House said that more than 20,000 Russian troops have died and another 80,000 were wounded in five months of fighting in eastern Ukraine, particularly in Bakhmut.