The UN agency for Palestinian refugees (UNRWA) said six staffers were killed in Israeli airstrikes on a UN-run school in the central Gaza Strip on Wednesday.

At least 18 people were killed in two airstrikes on al-Jaouni School in the Nuseirat refugee camp on Wednesday, according to local health authorities.

Among the victims was the manager of the UNRWA shelter, the UN agency said.

“This is the highest death toll among our staff in a single incident,” UNRWA said.

Wednesday’s Israeli attack was the fifth to have hit the school, where around 12,000 displaced civilians have sheltered, since Oct. 7, 2023.

“No one is safe in Gaza No one is spared,” UNRWA said. “Schools and other civilian infrastructure must be protected at all times, they are not a target.”

Israel has systematically targeted civilian facilities, including schools, hospitals, and places of worship, amid its ongoing offensive on the Gaza Strip.

Under the rules of war, targeting such civilian facilities can constitute a war crime.

Last month, at least 100 people were killed and dozens injured in an Israeli strike on the Al-Taba’een School in Gaza City, where over 6,000 displaced people have sheltered.

Israel has continued its brutal offensive on Gaza since a cross-border incursion last October by the Palestinian group Hamas, despite a UN Security Council resolution demanding an immediate cease-fire.

Nearly 41,100 people, mostly women and children, have since been killed and more than 95,000 injured, according to local health authorities.

The Israeli onslaught has displaced almost the entire population of the territory amid an ongoing blockade that has led to severe shortages of food, clean water and medicine.

Israel faces accusations of genocide for its actions in Gaza at the International Court of Justice.