Friday, Russia and Ukraine accused each other of bombarding a prison in a separatist part of eastern Ukraine. This action purportedly killed hundreds of Ukrainian prisoners of war seized following the fall of Mariupol, the city whose troops famously withstood a months-long Russian siege.

Both sides claimed that the attack was deliberate to conceal atrocities.

Russia asserted that the Ukrainian military used US-supplied rocket launchers to attack a prison in Olenivka, a settlement controlled by the Donetsk People's Republic, backed by Russia. According to separatist authorities and Russian officials, the strike killed 53 Ukrainian prisoners of war and wounded 75 more.

Moscow initiated an inquiry into the attack by dispatching a team from Russia's Investigative Committee, the country's primary criminal investigation agency, to the scene. State-run RIA Novosti said that remnants of precision High Mobility Artillery Rocket System rockets supplied by the United States were discovered at the location.

The Ukrainian military denied launching any rockets or artillery at Olenivka and accused the Russians of bombarding the prison to cover up the suspected torture and execution of Ukrainians. A representative for Ukrainian President Volodymyr Zelensky denounced the bombardment as a "deliberate, cynical, and calculated massacre of Ukrainian prisoners."

Both claims could not be independently confirmed.

The Associated Press captured footage of charred, twisted bed frames in the ruined barracks and burning bodies and sheets of metal dangling from the roof. The footage also depicted a line of dead lined up next to a barbed-wire fence and a collection of alleged metal missile bits on a wooden seat.

The leader of the internationally unrecognized Donetsk republic, Denis Pushilin, stated that the prison contained 193 detainees. He did not disclose the number of Ukrainian prisoners of war.

Eduard Basurin, the deputy leader of the Donetsk separatist forces, stated that the Ukrainian government intended to bomb the prison to prevent prisoners from exposing vital military information.

Ukraine "knew precisely where and how they were being held," he claimed. "After Ukrainian prisoners of war began to discuss the crimes they had committed and the orders they had received from Kiev, the political leadership of Ukraine decided to launch a strike here,"

The adviser to the Ukrainian president, Mykhailo Podolyak, demanded a "rigorous investigation" and asked the United Nations and other international organizations to denounce the attack. He said a few days before the attack, the Russians transferred some Ukrainian captives to the barracks, indicating that it was premeditated.

Ukrainian officials asserted that Russia's Wagner Group, mercenaries that Russia has reportedly employed in prior armed conflicts and elsewhere in Ukraine, was responsible for the attack.

The Ukrainian security agencies published a statement stating evidence suggesting Russia was responsible, such as the transfer of prisoners, the examination of injuries and the blast wave, intercepted phone conversations, and the absence of shelling at the scene.

According to the statement, the explosion in Olenivka was a Russian terrorist attack and a flagrant breach of international agreements.

Lieutenant-General Igor Konashenkov, a Russian Ministry of Defense spokesman, described the attack as a "bloody provocation" intended to discourage Ukrainian soldiers from surrendering. He further stated that HIMARS rockets supplied by the United States were employed, and eight guards were among the injured.

Russia's embassy in the United Kingdom stated on Friday that soldiers from the Azov battalion, which played a crucial role in the Mariupol battle, should be executed.

"[Azov] militants deserve to be executed, but not by firing squad but by hanging, as they are not genuine troops. They are deserving of a shameful death," the embassy tweeted.

The Ukrainian army is trying to maintain control over the remaining Donetsk territory. Together with the neighboring province of Luhansk, they comprise Ukraine's predominantly Russian-speaking industrial Donbas area.

For several months, Moscow's primary objective has been to conquer areas of the Donbas not already occupied by separatists.

Holding POWs in a location with ongoing fighting looked to violate the Geneva Convention, which requires detainees to be transported to camps outside combat zones as soon as feasible after capture.

Among the Ukrainian POWs incarcerated in Donetsk were soldiers seized at the fall of Mariupol. They spent months with residents locked up in a massive steel plant in the southern port city. Their defiance in the face of a persistent Russian bombardment symbolized Ukrainian resistance to Russian aggression.

In May, more than 2,400 soldiers from the Azov Regiment of the Ukrainian national guard and other military formations surrendered on orders from the Ukrainian military.

Countless Ukrainian soldiers have been imprisoned in Russian-controlled territory. Families of other POWs do not know if their loved ones are still alive or if they will ever return home.