It was unclear who was overseeing the convoy. Philippe Lazzarini, the head of the main U.N. aid group that serves Palestinians, said that no U.N. agency was involved and the Israeli military said the aid was to be distributed by “private contractors.”

Lawlessness is rampant in many parts of northern and southern Gaza, residents and aid officials say, with no authority emerging to take charge of public order after Israel’s ouster of Hamas forces in those areas.

The World Food Program said last week that it has paused food deliveries to northern Gaza because of the challenges of safely delivering aid there.

Mr. Lazzarini said on Sunday that UNRWA, whose funding has been suspended by several donor nations since the U.N. launched an investigation into about a dozen employees accused of participating in the Oct. 7 attacks, was last able to deliver aid to northern Gaza over a month ago.

In recent weeks, large crowds of Gazans have repeatedly rushed aid convoys, and seized supplies, occasionally while armed. Some Gazan police officers have refused to guard the convoys because they fear their affiliation with the Hamas-run government makes them targets of Israeli troops, Western officials say.

A Hamas official, Izzat Al-Rishq, blamed Israel for the deaths and said that Hamas would not allow negotiations aimed at stopping the war to be used as “a cover for the enemy’s continued crimes against our people in the Gaza Strip.”

The Palestinian Authority, which controls parts of the Israeli-occupied West Bank, called the deaths a “heinous act” by Israeli forces and demanded that the international community, especially Israel’s chief ally, the United States, intervene to stop Israel’s offensive.

Matthew Miller, a State Department spokesman, said the United States was “urgently seeking additional information on exactly what took place” and had been in touch with the Israeli government since early Thursday about its investigation into the deaths.

“We will be monitoring that investigation closely and pressing for answers,” he said.