Ukraine has asked for permission for the Red Cross and the UN to look into the deaths of over 50 Ukrainian POWs during an offensive in an occupied area.
In order to assist with the evacuation and treatment of the injured, the Red Cross stated that it is requesting entry to the jail.
Both Russia and Ukraine have claimed responsibility for assaulting the camp.
Unconfirmed Russian video footage from the scene depicts a jumble of demolished bunk beds and severely burned victims.
It is still unclear exactly what occurred in the prison camp at Olenivka, which is run by the separatist Donetsk People's Republic and supported by Russia.
Russia allegedly targeted the location in an effort to obliterate evidence of murder and torture, according to Ukraine. The incident was referred to as a "deliberate Russian war crime" by President Volodymyr Zelensky.
Russia said that Ukrainian precision missiles had struck the camp.
Members of the Azov battalion, who were taken in May while defending the southern city of Mariupol and whom Russia has attempted to portray as neo-Nazis and war criminals, are reportedly among those incarcerated inside the prison.
The so-called Donetsk People's Republic spokesperson, Daniil Bezsonov, said that the strike had been a "direct hit on a barracks containing detainees."
The attack, according to Russia's defense ministry, was carried out with US-produced Himars artillery, and Ukraine was charged with having "deliberately committed" the provocation. The ministry displayed pieces of what it claimed to be Himars system rockets.
However, Ukraine disputed the existence of any artillery or rocket attacks.
A missile attack would have dispersed the dead, according to a presidential aide who stated the scene seemed to have been set on fire.
The general staff of the Ukrainian armed forces requested an investigation into the killings from the UN and the Red Cross, alleging that Russia had targeted the camp to conceal its treatment of POWs.
It said on social media that they should reply right away since the two organizations had promised to keep the prisoners of war secure there.
The Red Cross said it was requesting entry to the area and has volunteered to assist in the injured's evacuation.
According to a statement from the organization, "our first concern right now is ensuring that the injured receive life-saving treatment and that the corpses of those who lost their lives are treated with dignity."
Andriy Kostin, the new prosecutor general of Ukraine, had declared that he had launched a war crimes inquiry into the explosion.
Who was responsible for this war crime?
Paul Adams from Kiev
Hellish conditions prevail within the "filtration camp" next to Olenivka".
A tangle of metal bunk beds and an unknown number of burnt victims are visible through jagged holes in the corrugated iron ceiling, some of which are still lying in their likely sleeping positions.
Outside, other victims are bloodied but not burnt, and there is blood on a wooden pallet. They appear starved.
There isn't much anyone can do right now to independently verify the conflicting statements as independent journalists are unable to access the website. The separatists who are supported by Russia, according to Ukraine, spoke of a string of purposeful explosives that they themselves planned in radio communication that was intercepted. Other Ukrainian accounts place the blame on the Russian Wagner group mercenaries.
The only way to know the truth is to conduct a comprehensive inquiry with objective professionals. It's unlikely that these specialists will ever be given access to this horrific site.
On Friday morning, video of the carnage inside a dorm-like hangar packed with burned-out or wrecked bunk beds surfaced online. The video was obtained from Russia 1 on official television in Russia. Video of the building's devastation and bloodshed is then cut to.
The location of the inside and outdoor pictures cannot be independently confirmed by the BBC.
However, the Reality Check team at the BBC has determined that the outside photos of the structure match Prison No. 120, which is close to Olenivka.
Prior to February 2022, the jail was abandoned and only used for POWs and civilians who failed Russian filtering, a method in which suspects are interrogated before a decision is made about where to send them.
A number of the men from the nationalist Azov Battalion, according to Andriy Biletskyi, one of the unit's founders, were slain.
It has been shown that several Ukrainian soldiers who gave themselves up to Russian forces during a drawn-out siege at the Azovstal steel facility in Mariupol were transported to Olenivka.
The soldiers had resisted a persistent Russian assault on the vast facility for weeks before giving up in May, taking cover in the plant's network of tunnels from artillery and airstrikes.
According to Ukrainian officials, prisoners of war in Olenivka were tortured.
Friday's disturbing web video showing a prisoner of war being castrated in another region of the Russian-occupied Donbas sparked even more indignation in Ukraine.
The Russian soldier who was seen on camera carrying out the attack in Severodonetsk was later revealed to be a member of Ramzan Kadyrov's militia.
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