Palestinians check a UN-school housing displaced people that was hit during Israeli bombardment in Nuseirat, in the central Gaza Strip. AFP
"Another UNRWA school turned shelter attacked," Philippe Lazzarini wrote on social media platform X, of the school in the Nuseirat area of central Gaza.
The Al-Aqsa Martyrs Hospital said at least 37 people were killed in the strike.
Lazzarini said the school was sheltering 6,000 displaced people when it was hit.
He added that UNRWA "shares the coordinates of all its facilities (including this school) with the Israeli army and other parties in the conflict".
"Attacking, targeting or using UN buildings for military purposes is a blatant disregard of International Humanitarian Law," Lazzarini said.
Israeli rights group B'Tselem called the strike a "suspected war crime".
"If, as Israel claims, Hamas used the school to plan military operations, this action is illegal, but it cannot justify the massive harm to civilians who sought shelter in the school from the horror of prolonged fighting," the group said in a statement.
"As demonstrated throughout the war, the killing of civilians is an unavoidable result of the character of Israel's military activity in the Gaza Strip," it said, urging the international community to help stop the fighting.
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