The United Nations announced on Monday that it would reduce its presence in Gaza by withdrawing about a one-third of its international workers there, following repeated strikes of its facilities by Israel.

Secretary General António Guterres said in a statement that the decision to reduce the organization’s footprint in Gaza was “difficult” at a time when humanitarian needs were soaring and as a resumption of Israeli attacks were killing hundreds of Palestinians, including women and children.

The drawdown announced Monday would be the first time since the start of the Israeli-Hamas war in 2023 that the United Nations has reduced its work force in Gaza, but it will retain a presence there.

“The U.N. is not leaving Gaza. The organization remains committed to continuing to provide aid that civilians depend on for their survival and protection,” Mr. Guterres said in the statement.

At least 280 U.N. staff members have been killed in Gaza since the start of the war, the organization’s largest loss of life in any conflict in its history, Mr. Guterres has said.

Stéphane Dujarric, the U.N. spokesman, said that about 30 percent of the organization’s 100 or so international staff members from different agencies would be leaving Gaza over the next week and that likely more would depart in the coming weeks.

Local Palestinian staff members would remain in Gaza to carry out humanitarian work.

On March 19, an Israeli tank shell hit a U.N. compound located in the Deir al Balah neighborhood of Gaza, Mr. Dujarric said. The attack killed a U.N. staff member from Bulgaria and injured six others.

“The point is that the Israelis knew exactly where this U.N. facility was, and it was hit by a shell from one of their tanks,” Mr. Dujarric said. He said the United Nations wanted an independent investigation and called on all warring parties to respect international laws protecting U.N. premises and humanitarian workers.

“An initial investigation into this incident found no connection to the I.D.F.,” said Jonathan Harounoff, Israel’s U.N. spokesman. He added: “Our only targets are Hamas terrorists whose raison d’être is to kill and kidnap Israelis, to use Gazans as human shields and to use U.N. facilities as launching pads and weapon depots.”

The United Nations has alleged that Israel has targeted its compounds, convoys and workers on multiple occasions in Gaza.

Israel has blocked all humanitarian aid into Gaza since March 2, and with the border crossings closed, no food, medicine, fuel or clean water has entered the strip where two million people rely on essential aid for weeks.

Israel said that it had blocked aid and resumed airstrikes, shattering a fragile cease-fire agreement with Hamas, because the militant group, which led the Oct. 7, 2023, assault on Israel that started the war, had refused to release the remaining hostages it had seized. Of the 59 remaining hostages in Gaza, fewer than half are believed to be alive.

Mr. Dujarric said that Israeli strikes had also targeted ambulances and medical workers who were trying to save survivors of airstrikes.