A destroyed barrack at a prison in Olenivka, in an area controlled by Russian-backed separatist forces, eastern Ukraine, Friday. Russia and Ukraine accused each other Friday of shelling a prison in a separatist region of eastern Ukraine, an attack that reportedly killed dozens of Ukrainian military prisoners who were captured after the fall of a southern port city of Mariupol in May. Associated Press

KYIV, Ukraine — A request by the International Committee of the Red Cross to visit a shelled prison where dozens of Ukrainian prisoners of war died went unanswered Saturday, as Ukrainian and Russian officials continued to blame each other for the attack on a prison in a separatist-controlled area.

The ICRC asked to visit the prison to make sure the scores of wounded POWs had proper treatment, but said that as of late Saturday their request had not been granted.

Meanwhile, Russia kept on launching attacks on several Ukrainian cities, hitting a school and a bus station.

Ukrainian President Volodymyr Zelenskyy said the ICRC and the United Nations have a duty to react after the shelling Friday of the prison complex in Ukraine’s eastern Donetsk province.

“It was a deliberate Russian war crime, a deliberate mass murder of Ukrainian prisoners of war,” Zelenskyy said in a video address late Friday. “There should be a clear legal recognition of Russia as a state sponsor of terrorism.”

Separatist authorities and Russian officials said the attack killed 53 Ukrainian POWs and wounded another 75. Russia’s Defense Ministry on Saturday issued a list naming 48 Ukrainian fighters, aged 20 to 62, who died in the attack; it was not clear if the ministry had revised its fatality count.

The ICRC has organized civilian evacuations and worked to monitor the treatment of POWs held by Russia and Ukraine. “Our priority right now is making sure that the wounded receive lifesaving treatment and that the bodies of those who lost their lives are dealt with in a dignified manner,” the Red Cross said.

“Granting ICRC access to POWs is an obligation of parties to conflict under the Geneva Conventions,” the ICRC said on Twitter. “We will not stop seeking access to these POWs and to all POWs of this international armed conflict who we have not had access to yet.”

Both Ukraine and Russia alleged the attack on the prison was premeditated and intended to silence the Ukrainian prisoners and destroy evidence.

Russia claimed Ukraine’s military used U.S.-supplied precision rocket launchers to target the prison in Olenivka, a settlement controlled by the Moscow-backed Donetsk People’s Republic.

The Ukrainian military denied making any rocket or artillery strikes in Olenivka. It accused the Russians of shelling the prison to cover up the alleged torture and execution of Ukrainians there.

The Institute for the Study of War, a think tank based in Washington, said the competing claims and limited information prevented assigning full responsibility for the attack but the “available visual evidence appears to support the Ukrainian claim more than the Russian.”

Moscow has opened a probe into the attack on the prison and the United Nations said it also was prepared to send investigators. U.N. deputy spokesman Farhan Haq said “we stand ready to send a group of experts able to conduct an investigation, requiring the consent of the parties, and we fully support the initiatives” of the Red Cross.

Elsewhere in eastern Ukraine, Russian rockets hit a school in Kharkiv, the country’s second-largest city, overnight, and another attack occurred an hour later, Mayor Ihor Terekhov said Saturday. There were no immediate reports of injuries.

The bus station in the city of Sloviansk also was hit, according to Mayor Vadim Lyakh. Sloviansk is near the front line of fighting as Russian and separatist forces try to take full control of the Donetsk region, one of two eastern provinces that Russia has recognized as sovereign states.

Deputy Prime Minister Iryna Vereshchuk warned Saturday that Ukrainian-controlled parts of the Donetsk region will face severe heating problems this winter because of the extensive destruction of gas mains. She called for a mandatory evacuation of residents before the cold weather sets in.

In southern Ukraine, one person was killed and six injured in shelling that hit a residential area in Mykolaiv, a port city, the regional government said.

Friday’s attack on the prison reportedly killed Ukrainian soldiers captured in May after the fall of Mariupol, a Black Sea port city where troops and the Azov Regiment of the national guard famously held out against a months-long Russian siege.

On Saturday, an association of Azov fighters’ relatives dressed in black held a demonstration outside Kyiv’s St. Sophia Cathedral and called for Russia to be designated a terrorist state for violating the Geneva Convention’s rules for the treatment of war prisoners.

A woman wearing dark glasses who gave only her first name, Iryna, was waiting for news of her 23-year-old son.

“I don’t know how is he, where is he, if he is alive or no. I don’t know. It’s a horror, only horror. For a mother, it’s the biggest loss if her child has gone,” she said.

On the energy front, Russia’s state-owned natural gas corporation said Saturday it has halted shipments to Latvia because of contract violations. Gas giant Gazprom said the shipments were stopped because Latvia broke “terms for extraction of gas.” It did not elaborate.

The statement likely referred to a refusal to meet Russia’s demand for gas payments in rubles rather than other currencies. Gazprom has previously suspended gas shipments to other EU countries, including the Netherlands, Poland and Bulgaria, because they would not pay in rubles.

EU nations have been scrambling to secure other energy sources, fearing that Russia will cut off more gas supplies as winter approaches.