Six staff members with the UN agency that assists Palestine refugees (UNRWA) were killed in Gaza on Wednesday when two Israeli airstrikes hit a school-turned-shelter and its surroundings.
“This is the highest death toll among our staff in a single incident,” UNRWA said in a post on the social media platform, X.
At least 34 people were killed in the strikes, according to media reports.
UNRWA said the shelter manager and other team members were among the victims.
UN Secretary-General António Guterres deplored the bloodshed.
“What’s happening in Gaza is totally unacceptable,” he wrote on X.
“These dramatic violations of international humanitarian law need to stop now.”
The UNRWA school in Nuseirat, located in the Middle Area of the Gaza Strip, was sheltering around 12,000 displaced people, mainly women and children.
This marked the fifth time that it had been hit since the conflict began 11 months ago.
Earlier on Wednesday, the UN said the site had been previously deconflicted with the Israeli forces.
UNRWA called on all parties to the conflict to never use schools or the areas around them for military or fighting purposes.
“No one is safe in Gaza. No one is spared. Schools and other civilian infrastructure must be protected at all times, they are not a target,” the tweet said.
UNRWA Commissioner-General Philippe Lazzarini lamented the “endless and senseless killing, day after day” in Gaza.
Writing on X, he said at least 220 agency staff have lost their lives since the war began.
“Humanitarian staff, premises and operations have been blatantly and unabatedly disregarded since the beginning of the war,” he said.
He warned that “the longer impunity prevails, the more international humanitarian law and the Geneva conventions will become irrelevant.”
In a related development, the UN reported that health workers continue efforts to vaccinate young children in northern Gaza against polio, part of a wider campaign to defeat the disease, which can cause paralysis.
More than 81,600 boys and girls were vaccinated as of Tuesday, according to preliminary data from the World Health Organisation (WHO).
Polio was detected in Gaza in June and UN agencies and partners launched a two-round campaign this month to provide over 640,000 children with two doses of novel oral polio vaccine type 2.
So far, nearly 528,000 children have been reached in the first round.