The United States says it has approved $30m in direct funding for the controversial Israel-backed group delivering aid in Gaza, despite growing concern over a series of deadly attacks on Palestinian aid seekers near its distribution hubs in the besieged territory.

“We call on other countries to also support the GHF, the Gaza Humanitarian Foundation, and its critical work,” State Department spokesperson Tommy Pigott told reporters on Thursday.

The GHF, backed by the US and Israel, has been a source of widespread criticism since its establishment in May. The organisation was set up amid growing pressure on Israel to ease its months-long total blockade on humanitarian aid entering the Strip. The blockade had pushed most of Gaza’s population to the brink of starvation.

International aid groups and the United Nations have refused to work with the GHF, saying it violates basic humanitarian principles by coordinating delivery with Israeli troops backed by privately hired and armed US security personnel.

Video clips have emerged showing Palestinians being shot at while trying to collect food aid.

At least 549 Palestinians have been killed while waiting for food aid distributed at GHF sites, the Gaza Government Media Office said on Thursday. The GHF, which is officially a private group, has denied that deadly incidents have occurred in the immediate vicinity of its aid points.

The GHF’s interim executive director, John Acree, welcomed the US contribution and said it was “time for unity and collaboration”.

“We look forward to other aid and humanitarian organizations joining us so we can feed even more Gazans, together,” he said in a statement.

Asked about the criticism of the operation, Pigott said the group has distributed 46 million meals so far, which is “absolutely incredible” and “should be applauded”.

The financial support to the GHF is part of President Donald Trump and Secretary of State Marco Rubio’s “pursuit of peace in the region”, he said.

‘Nothing but death’

A witness who has tried unsuccessfully to receive aid from the distribution sites on several occasions described the nightmarish conditions he faced when attempting to reach the hubs.

Atar Riyad, a father of eight originally from Beit Hanoon who has been displaced to Gaza City, told Al Jazeera he had travelled towards the distribution centres near the so-called Netzarim Corridor in central Gaza several times. Thousands of hungry Palestinians would gather near the sites early in the morning, Riyad said.

He said that on one occasion, he saw trucks running over aid seekers. On another, he saw the bodies of young people who appeared to have been shot.

“We went to only find death in front of us. There was nothing but death,” he said.

Riyad said his best friend and neighbours were among those who had been killed at the distribution centres. “All died as they tried to get food to feed their families,” he said.

Kate Mackintosh, executive director of the UCLA Law Promise Institute Europe, told Al Jazeera that GHF workers could bear criminal liability for the killings of aid seekers near the group’s distribution points.

“It’s very unclear why these people are being targeted and killed, but I think it’s pretty clear that these are unarmed civilians who are desperately trying to get food for their families,” she said.

“Firing upon people in that situation prima facie is a war crime.”

She said that people working for the GHF would “have to think about the extent to which they could be complicit in those crimes”.

“If they’re aware that this is going to happen – or even in some jurisdictions they’re aware of the substantial risk of this happening, which it seems they must be … they could be held criminally liable for participating in those crimes.”

In the latest violence surrounding the distribution of food, an Israeli strike on Thursday hit a street in central Gaza, killing 18 people.

Witnesses said a crowd of people had gathered to receive bags of flour from a Palestinian police unit that had confiscated the goods from gangs looting aid convoys.

Efforts by the UN to distribute the food have been plagued by armed gangs looting trucks and by crowds of desperate people offloading supplies from convoys.

The strike in the central town of Deir el-Balah on Thursday appeared to target members of Sahm, a security unit tasked with stopping looters and cracking down on merchants who sell stolen aid at high prices. The unit is part of Gaza’s Hamas-led Interior Ministry but includes members of other factions.

Israel has accused the Hamas group of stealing aid and using it to prop up its rule in the enclave. Israeli forces have repeatedly struck Gaza’s police, considering them a branch of Hamas.