World leaders have called for an investigation and a ceasefire nearly five months into the Gaza war after dozens of desperate Palestinians were killed rushing an aid convoy.

Vowing to "do more" to address the worsening humanitarian situation, President Joe Biden said Friday that the United States would start delivering relief supplies into Gaza via air drops -- as some of its allies have already -- in a bid to get aid into hard-to-reach areas.

Israeli troops opened fire as Palestinian civilians scrambled for food supplies during a chaotic melee on Thursday that the Hamas-run territory's health ministry said killed more than 100 people in Gaza City.

The deaths came after a World Food Programme official had warned: "If nothing changes, a famine is imminent in northern Gaza."

The Israeli military said a "stampede" occurred when thousands of Gazans surrounded the convoy of 38 aid trucks, leading to dozens of deaths and injuries, including some who were run over.

An Israeli source acknowledged troops had opened fire on the crowd, believing it "posed a threat".

Gaza's health ministry called it a "massacre", and said 115 people were killed and more than 750 wounded.

A UN team that visited some of the wounded in Gaza City's Al-Shifa Hospital on Friday saw a "large number of gunshot wounds", UN chief Antonio Guterres's spokesman said.

The hospital received 70 of the dead and treated more than 700 wounded, of whom around 200 were still there during the team's visit, spokesman Stephane Dujarric said.

"I'm not aware that our team examined the bodies of people who were killed. My understanding from what they saw in terms of the patients who were alive getting treatments is that there was a large number of gunshot wounds," he said.

The aid convoy deaths helped push the number of Palestinian war dead in Gaza to 30,228, mostly women and children, according to the latest toll from the territory's health ministry.

The war began on October 7 with an unprecedented Hamas attack on southern Israel that resulted in the deaths of about 1,160 people, mostly civilians, Israeli figures show.

Israel's military says 242 soldiers have died in Gaza since ground operations began in late October.

- US to 'insist' on more aid -

"The Israeli army must fully investigate how the mass panic and shooting could have happened," German Foreign Minister Annalena Baerbock wrote on social media platform X.

Her French counterpart Stephane Sejourne said: "There will have to be an independent probe to determine what happened".

European Commission chief Ursula von der Leyen, meanwhile, said that "every effort must be made to investigate what happened and ensure transparency".

Aerial footage of the incident made clear "just how desperate the situation on the ground is", a US State Department spokesman said.

Despite warnings from within his administration that air drops "are a drop in the bucket" compared with what is needed, Biden said Washington would begin deliveries from the sky "in the coming days".

"We need to do more, and the United States will do more," he told reporters at the White House.

Biden said Thursday's deaths happened because Gazans were "caught in a terrible war, unable to feed their families", adding he would "insist" Israel let in more aid trucks.

Reacting to the announcement, the International Rescue Committee (IRC) said the very fact air drops were "being considered is testament to the serious access challenges in Gaza".

"Air drops are not the solution to relieve this suffering, and distract time and effort from proven solutions to help at scale," it added, calling for a "sustained ceasefire" and for land crossings into Gaza to be reopened to aid shipments.

US official Samantha Power, who oversees USAID, told reporters in Ramallah that an average of just 96 aid trucks were entering Gaza each day -- "a fraction of what is needed."

The aid convoy deaths dealt a blow to efforts to broker a new truce in Gaza to get more aid in and free the remaining Israeli hostages held by Palestinian militants.

Militants took about 250 hostages on October 7, 130 of whom remain in Gaza, including 31 that Israel says are presumed dead.

Biden had previously said the convoy deaths would complicate truce talks, but told reporters Friday he was still "hoping" for a deal by the Muslim holy month of Ramadan -- starting on March 10 or 11, depending on the lunar calendar -- though he acknowledged it remained uncertain.

"We'll get there, but we're not there yet -- we may not get there," he said, without elaborating, as he headed to his helicopter.

Late on Thursday, he discussed the convoy deaths with the leaders of fellow truce mediators Egypt and Qatar, the White House said, adding the incident "underscored the urgency of bringing negotiations to a close".

US plans aid air drops in Gaza

President Joe Biden said Friday that the United States would start to deliver relief supplies from the air into Gaza, a day after the deaths of more than 100 Palestinians at an aid convoy.

"We need to do more, and the United States will do more," Biden told reporters at the White House at the start of a meeting with Italian Prime Minister Giorgia Meloni.

"In the coming days we're going to join with our friends in Jordan and others in providing air drops of additional food and supplies," the 81-year-old Biden said in the Oval Office.

The announcement comes as negotiations continue for a ceasefire between Israel and Hamas, amid a humanitarian crisis in Gaza which has been under siege since Hamas's October 7 attacks on Israel.

Biden has pushed Israel to reduce civilian casualties and allow aid in, while at the same time he has maintained military assistance for the key US ally.

Biden said later he was "hoping" for a deal on a six-week ceasefire by the Muslim holy month of Ramadan, which will start on March 10 or 11, depending on the lunar calendar.

"We'll get there but we're not there yet -- we may not get there," Biden added, without elaborating, as he headed to his helicopter to spend the weekend at the presidential Camp David retreat.

Ceasefire talks have been complicated by Thursday's incident in which dozens of desperate Palestinians were killed rushing an aid convoy in northern Gaza, where the UN has warned of famine.

An Israeli source acknowledged troops had opened fire on the crowd, believing it "posed a threat."