"Bilogorivka (village) was hit in an air strike" on Saturday, said Sergii Gaidai.

"The bombs fell on the school and unfortunately it was completely destroyed. There was a total of 90 people, 27 were saved," he said on Telegram. "Sixty people who were in the school are very probably dead."

Rescuers could not work overnight because of a threat of new strikes, but resumed their work Sunday.

Amin Awad, the United Nations Ukraine crisis coordinator, said he was "profoundly shocked" by reports of the incident.

"The attack, which reportedly left dozens of people dead, is yet another stark reminder of the cruelty of this war," he added.

"My thoughts are with the victims and their families."

Rescuers were also looking for survivors in the neighbouring village of Shepilivka after a strike hit a house where 11 people were sheltering in the basement, he said.