Gaza’s Civil Defence spokesperson Mahmud Bassal said 18 people were killed in the strike on al-Jaouni school in Nuseirat refugee camp, which is being used as a shelter by thousands of displaced Palestinians.
Israel’s military says it carried out a precise strike on terrorists planning attacks from the school, and that it had taken measures to avoid harm to civilians.
UN Secretary General Antonio Guterres said the attack amounted to dramatic violations of international humanitarian law in a post on X.
In July, 16 people were reportedly killed in a strike which the Israeli military said had targeted several structures at the school used by Hamas fighters.
Hamas – which is proscribed as a terrorist group by Israel, the UK and other countries – has denied using schools and other civilian sites for military purposes.
Israel’s ambassador to the UN, Danny Danon, hit out at Guterres’ criticism of the strike and said it was unconscionable that the UN continues to condemn Israel in its just war against terrorists.
Israeli forces launched a campaign to destroy Hamas in response to the group’s unprecedented attack on southern Israel on 7 October, in which about 1,200 people were killed and 251 others were taken back to Gaza as hostages.
More than 41,080 people have been killed in Gaza since then, according to the territory’s Hamas-run health ministry.
UN spokesman Stéphane Dujarric told reporters the UN condemned “all air strikes that target civilians and those that also target UN facilities”