The UN agency for Palestinian refugees (UNRWA) says more than 50,000 children in the Gaza Strip require immediate medical treatment for acute malnutrition.

In a statement on Saturday, the agency noted “with continued restrictions to humanitarian access, people in Gaza continue to face desperate levels of hunger. UNRWA teams work tirelessly to reach families with aid, but the situation is catastrophic”.

UNICEF spokesperson James Elder also described how difficult it is to not only get aid into Gaza, but also to distribute it across the war-battered coastal enclave.

“More aid workers have been killed in this war than any war since the advent of the UN,” he told Al Jazeera.

On Wednesday, UNICEF had a mission to drive a truck full of nutritional and medical supplies for 10,000 children, Elder said. Their task was to deliver the aid, which was pre-approved by Israeli authorities, from Deir el-Balah to Gaza City, a 40km (25 miles) round trip.

“It took 13 hours and we spent eight of those around checkpoints, arguing around paperwork – ‘was it a truck or a van’,” he said.

“The reality is this truck was denied access. Those 10,000 children did not get that aid … Israel as the occupying power has the legal responsibility to facilitate that aid.”

One of the main land crossings in Rafah has been closed since Israeli forces seized the area early last month. The move has heightened fears of famine in southern and central Gaza.

The UN’s World Food Programme Deputy Executive Director Carl Skau spent two days assessing the plight of Palestinians this week, saying the challenges are “like nothing I have ever seen”.

”The situation in southern Gaza is quickly deteriorating. One million people in southern Gaza are trapped without clean water or sanitation in a highly congested area along the beach in the burning summer heat. We drove through rivers of sewage,” said Skau.

For months, right-wing Israelis have been protesting and blocking roads to prevent aid shipments from reaching Gaza, further straining the flow of desperately needed aid to the territory.

On Friday, the United States imposed sanctions on a “violent extremist” Israeli group for blocking and damaging humanitarian aid convoys to Gaza. The Group of Seven leaders also stressed UN agencies must work unhindered in Gaza.

UNRWA, which coordinates nearly all aid to Gaza, has also been in crisis since January, when Israel accused about a dozen of its 13,000 Gaza employees of being involved in the October 7 Hamas attack on Israel.

This claim led many nations, including top donor the US, to abruptly suspend funding to the agency, threatening its efforts to deliver aid.

UNRWA chief Philippe Lazzarini has repeatedly said Israeli moves to suspend funding are “additional collective punishment” for Palestinians already reeling from nonstop Israeli bombardment.