Israeli forces in war-torn Gaza opened fire on Palestinians scrambling for food aid in a chaotic melee on Thursday that the health ministry in the Hamas-run territory said killed more than 100 people.
The Israeli military said a "stampede" occurred when thousands of Gazans surrounded a convoy of 30 aid trucks, leading to dozens of deaths and injuries, including some who were run over by the lorries.
An Israeli source acknowledged troops had opened fire on the crowd, believing it "posed a threat".
The Gaza health ministry condemned what it called a "massacre" before dawn in Gaza City in which 104 people were killed and more than 750 others wounded.
The incident adds to a Palestinian death toll from the war which the ministry earlier Thursday said had topped 30,000, and dampens hopes a truce deal between Israel and Hamas militants could be just days away.
A witness in Gaza City said the violence unfolded when thousands of people desperate for food rushed towards aid trucks at the city's western Nabulsi roundabout.
"Trucks full of aid came too close to some army tanks that were in the area and the crowd, thousands of people, just stormed the trucks," the witness said, declining to be named for safety reasons.
"The soldiers fired at the crowd as people came too close to the tanks."
The office of Israeli Prime Minister Benjamin Netanyahu also said many of the dead were crushed by the trucks when they were "overwhelmed by people trying to loot".
Aerial images released by the Israeli army showed what it said were scores of Gazans surrounding aid trucks in Gaza City.
- 'Another day from hell' -
President Joe Biden said the United States was checking "two competing versions" of the incident.
When asked if the death toll was likely to complicate efforts by US and other mediators to broker a truce, Biden replied: "I know it will."
He said later that a ceasefire between Israel and Hamas was now unlikely to happen by Monday -- the timeline that he had predicted earlier this week.
UN humanitarian chief Martin Griffiths said he was "appalled at the reported killing and injury of hundreds of people during a transfer of aid supplies" and warned "life is draining out of Gaza at terrifying speed".
Saudi Arabia strongly condemned what it called the "targeting" of unarmed civilians. Italy called for an immediate ceasefire in Gaza to facilitate more humanitarian aid.
The UN Security Council will hold a closed-door emergency meeting on the incident on Thursday afternoon, which a diplomatic source said was requested by Algeria.
Looting of aid trucks had previously occurred in northern Gaza, where residents have taken to eating animal fodder and even leaves to try to stave off starvation, as aid groups warn of looming famine after nearly five months of war.
The chief of the United Nations agency for Palestinian refugees, UNRWA, said that no UN agency had been involved in Thursday's aid delivery, and called it "another day from hell".
- Truce hopes -
The war began on October 7 with an unprecedented Hamas attack on southern Israel that resulted in the deaths of around 1,160 people, mostly civilians, Israeli figures show.
Militants also took about 250 hostages, 130 of whom remain in Gaza, including 31 Israel says are presumed dead.
Israel's retaliatory military campaign has killed 30,035 people, according to the Hamas-run Gaza's health ministry.
Israel's military says 242 soldiers have died in Gaza since ground operations began in late October.
Washington, a key ally of Israel, has recently been pushing for a reduction in civilian casualties and a ceasefire.
It has been working with mediators from Egypt and Qatar to seek a six-week pause in the war.
Negotiators had hoped a truce could begin by around March 10 or 11 when the Muslim holy month of Ramadan begins, depending on the lunar calendar.
The proposals reportedly include the release of some Israeli hostages held in Gaza by militants in exchange for hundreds of Palestinians held in Israeli prisons.
Short of the complete withdrawal Hamas has called for, a source from the group said the deal might see Israeli forces leave "cities and populated areas", allowing the return of some displaced Palestinians and humanitarian relief.
- Fears of famine -
The World Food Programme has said Israel has blocked access for aid deliveries -- which Israeli officials have denied -- and warned that if nothing changes, "a famine is imminent in northern Gaza".
As fighting continued in Gaza, Muhammad Yassin, 35, battled to find flour in Zeitun.
"I found thousands of people waiting for long hours just to get a kilo (2.2 pounds) or two kilos of flour," he said.
"We have not eaten a loaf of bread for two months. Our children are starving."
In the south, nearly 1.5 million people trying to flee the fighting are now packed into Rafah city, also short of food, as Israel threatens to send in troops against Hamas fighters.
On Thursday, Israel's military said it had also killed militants in central Gaza as well as in Gaza City's Zeitun area, while intense fighting took place in Khan Yunis city just a few kilometres (miles) from Rafah.
A group of 150 Israelis have started a four-day march from Reim, near the Gaza border, to Jerusalem, calling for the government to reach a deal.
Violence has also surged in the occupied West Bank, where two Israelis were killed on Thursday.