Israel's 5th strike on same Gaza school 'totally unacceptable,' UN says

The Al-Jaouni School in Nuseirat in central Gaza was hit by Israeli forces for the fifth time in 11 months on Wednesday night, prompting furious complaints by United Nations leaders.

At least 17 people -- including six employees with the United Nations Relief and Works Agency for Palestine Refugees in the Near East, known as UNRWA -- were killed in the latest strike, according to the Hamas-run Gaza Civil Defense and UNRWA.

Al-Jaouni School -- like many others in the devastated territory -- doubles as a shelter for displaced Palestinians, and according to U.N. Secretary-General António Guterres was housing around 12,000 people when it was bombed. Before Wednesday's strike, the school was last attacked on July 6.

"What's happening in Gaza is totally unacceptable," Guterres wrote in a post on X, accusing Israel of "dramatic violations of international humanitarian law" over continued attacks on schools-turned-shelters in Gaza. The strikes "need to stop now," he added.

UNRWA Commissioner-General Philippe Lazzarini wrote on X: "Endless & senseless killing, day after day."

"Humanitarian staff, premises & operations have been blatantly & unabatedly disregarded since the beginning of the war," he added, noting at least 220 UNRWA staff have been killed in Gaza.

UNRWA confirmed Wednesday's strike as the deadliest single incident for agency staff since Oct. 7. The manager of the shelter was among those killed, it said.

"No one is safe in Gaza," the agency wrote on X. "No one is spared."

The Jordanian Foreign Ministry, meanwhile, "strongly" condemned the latest school bombing. "The protection of civilians and vital facilities that provide basic services to Palestinians, humanitarian facilities and shelters must be ensured," it said in a statement.

The Israel Defense Forces defended its strike, saying it targeted "a Hamas command and control center in the area." The Israeli army said it took steps to minimize civilian casualties.

The army wrote on social media on Thursday that nine of those killed -- including three of the dead UNRWA staffers -- were Hamas operatives. Two of those killed participated in Hamas' Oct. 7 attack, the IDF said. Neither were listed by the IDF as UNRWA staff.

Israel's Coordination of Government Activities in the Territories body dismissed U.N. criticism, hitting back at Lazzarini's post on X and alleging Gaza schools "have been Hamas weapons storage facilities, tunnel access points, and bases of operation for over a decade."

The latest strike on the Al-Jaouni School is one of many Israeli attacks on Gaza's schools since Oct. 7. In August, the U.N.'s human rights office accused Israel of "systematic attacks" on such facilities. An ABC News analysis found that at least 70% of schools in Gaza are visibly destroyed or damaged.

There were 25 strikes on schools serving as shelters -- including Al-Jaouni -- between Sept. 1 and June 1, in which 354 people were killed, according to individual tallies released by the Hamas-run Gaza Ministry of Health and collated by ABC News.

ABC News' Jordana Miller, Will Gretsky, Nasser Atta and Victoria Beaule contributed to this report.