The head of the United Nations agency supporting Palestinian refugees warned on Monday that a breakdown of civil order in Gaza had allowed widespread looting and smuggling, and blocked aid deliveries.

More than eight months of war have led to desperate humanitarian conditions in the besieged Palestinian territory and repeated UN warnings of man-made famine there.

"Gaza has been decimated," UNRWA chief Philippe Lazzarini told the agency's advisory body.

"We have witnessed unprecedented failures of humanity in a territory marked by decades of violence," he said, according to a written version of his closed-door address in Geneva.

"Palestinians and Israelis have experienced terrible losses and suffered immensely."

The war began after Hamas's October 7 attack inside Israel, which resulted in the deaths of 1,194 people, mostly civilians, according to an AFP tally based on official Israeli figures.

Israel's relentless retaliatory military campaign in Gaza since then has killed at least 37,626 people, also mostly civilians, according to the Hamas-run territory's health ministry.

Lazzarini warned that Gazans were in "a living hell, a nightmare from which they cannot wake".

- 'Catastrophic' hunger -

He highlighted "catastrophic levels of hunger" among Gaza's 2.4 million citizens, which he stressed were "the result of human action".

"Children are dying of malnutrition and dehydration, while food and clean water wait in trucks," he said.

UN agencies repeatedly warn of severe shortages of vital supplies in Gaza, exacerbated by restrictions on access by land and the closure of the key Rafah crossing with Egypt since Israeli forces seized the Palestinian side in early May.

Israel says it allows aid trucks in, trading blame with the UN over why the aid is stacking up.

The UN warns that the conflict and increasingly desperation among Gazans is causing civil order to collapse, making aid delivery even harder.

"The breakdown of civil order has resulted in rampant looting and smuggling that impede the delivery of desperately needed humanitarian aid," Lazzarini said.

- 'Relentless attacks' -

He said UNRWA, which coordinates nearly all aid to Gaza, was "staggering under the weight of relentless attacks".

The agency has been in crisis since January, when Israel accused about a dozen of its 13,000 Gaza employees of involvement in the October 7 attack.

A slew of probes, including one led by French ex-foreign minister Catherine Colonna, found some "neutrality-related issues" at UNRWA but stressed Israel had not provided evidence for its chief allegations.

The accusations prompted several countries to suspend funding to UNRWA.

Many -- although not top donor the United States -- have resumed payments but Lazzarini said funding woes persisted.

UNRWA has also suffered huge losses on the ground -- 193 employees killed and more than 180 facilities in Gaza damaged or destroyed since October 7.

Lazzarini condemned "a concerted effort to dismantle UNRWA".

He urged countries to "safeguard UNRWA's critical role".

"If the status quo is maintained," he warned, "the agency will crumble and millions of vulnerable children, women and men will pay a heavy price."