Russia said Ukraine used a U.S.-supplied rocket system to hit a detention facility near the eastern front lines, killing at least 40 soldiers including some who had been captured after the fall of Mariupol in late May.
Kyiv vehemently denied any such strike and said Moscow was to blame, accusing the Kremlin of deliberately shelling the prison to falsely accuse Ukraine of war crimes and cover up its own.
NBC News has not been able to independently verify the claims from either side.
Moscow-backed separatists in the Donetsk region said a Ukrainian attack on the prison in the town of Olenivka killed 53 prisoners of war and wounded 75 others. The Russian Defense Ministry said earlier that 40 had been killed, with 75 injured and eight staff members at the facility also wounded.
The victims included Ukrainian troops who had mounted a final defense at Mariupol's besieged Azovstal steel plant, the ministry said, accusing Kyiv of carrying out the strike to deter its troops from laying down their weapons in the future.
“Last night, the Kyiv regime purposefully committed a bloody provocation,” a statement on its official Telegram channel read Friday. The missile was launched from the American HIMARS multiple launch rocket system, the ministry said.
The self-proclaimed Donetsk People’s Republic said in a statement that 193 people were present in the building.
Ukraine’s military denied the accusation, saying the strike had been launched by Russian forces with the intention of framing Ukraine for war crimes and to “hide the torture of prisoners and executions” at the detention site.
“The Russian enemy continues its propaganda methods of conducting an information war in order to accuse the Armed Forces of Ukraine of shelling civilian infrastructure and the population, thus hiding its own insidious actions,” a statement from Ukraine's armed forces said Friday.
The Security Service of Ukraine said in a Telegram post that it had intercepted communications that would prove its forces were not responsible.
“The Kremlin puppets decided to commit another war crime,” said Oleksiy Arestovych, an adviser to Ukrainian President Volodymyr Zelenskyy, who was seemingly referring to the Moscow-backed separatist forces in Donetsk.
Ukraine’s foreign ministry, in a later statement, called for the International Criminal Court to “to immediately pay attention to the atrocities of Russian servicemen in the context of the investigation of war crimes and crimes against humanity.”
Russia has consistently denied targeting civilians or civilian areas throughout the war.
But accusations of atrocities committed by Russian forces have been leveled by Kyiv, its allies and human rights groups.
Ukrainian service members captured during the conflict who later spoke to NBC News described physical and emotional scars from torture, beatings and neglect at the hands of Russian forces.
International law provides protection for prisoners of war, with the Geneva Conventions decreeing that they must be treated humanely, protected against acts of violence, as well as intimidation and insults.
The apparent deadly strike overshadowed Kyiv’s efforts to herald its efforts to export grain for the first time since the Russian invasion brought a blockade of its much-needed global food supplies. Zelenskyy visited a port in the southern Odesa region Friday to inspect a shipment being loaded onto a Turkish vessel.
Meanwhile, a court in Kyiv on Friday lowered a Russian soldier’s war crimes sentence from life imprisonment to 15 years after appeal, according to The Associated Press. Vadim Shyshimarin, 21, was convicted of killing a civilian in May, in the first war crimes trial against a Russian soldier since the conflict began.