Zelensky calls on international agencies to investigate POW attack

July 30 (UPI) -- Ukrainian President Volodymyr Zelensky has accused Russia of "deliberate mass murder" amounting to a "war crime" as pressure grew Saturday for international agencies to investigate an attack that killed dozens of prisoners of war.

The attack destroyed a prison in the Donbas region Friday, killing nearly 60 Ukrainian prisoners who had been captured at the outset of the lengthy siege of Mariupol.

"Russia has proven with numerous terrorist attacks that it is the largest source of terrorism in the world today -- it is a fact," Zelensky charged in an overnight address, as reported by the Kyiv Independent.

He added: "It was a deliberate Russian war crime, a deliberate mass murder of Ukrainian prisoners of war."

Most of the soldiers at the facility had been captured in May as they defended the Azovstal steelworks that served as Ukraine's last stronghold in Mariupol.

On Friday, Russian officials attempted to shift blame and accused Ukraine of bombings its own soldiers. Kyiv replied that Moscow bombed the facility to cover up torture and brutal killings there.

Zelensky is now calling on international relief agencies to investigate.

"When the defenders of Azovstal left the plant, the United Nations and the International Committee of the Red Cross acted as guarantors of the life and health of our soldiers," Zelensky told reporters.

In a statement, the ICRC said it is aware of the attack and "has offered its support in the evacuation of the wounded and to donate medical supplies, protective equipment and forensic material."

"Our priority right now is making sure that the wounded receive life-saving treatment and that the bodies of those who lost their lives are dealt with in a dignified manner," the ICRC statement said.

Josep Borrell, the European Union's top diplomat, called the attacks "inhumane, barbaric acts" amounting to "severe breaches of the Geneva conventions and their additional protocol and amount to war crimes."

"The European Union condemns in the strongest possible terms the atrocities committed by the Russian armed forces and their proxies," Borrell said in a statement.

Meanwhile, residents of Kharkiv were bracing themselves on Saturday morning after a series of overnight missile attacks rocked the country's second-largest city.

First responders were able to extinguish a fire that broke out after a local college was struck by three of the missiles.

"The main building has been destroyed," the city's mayor, Ihor Terekhov, said on Telegram. "The fire was large but our firefighters have managed to extinguish it."

The mayor says missiles struck other parts of the city overnight, but there were no casualties.