UN Secretary-General Antonio Guterres on Thursday condemned the "endless catalogue of horrors" in Gaza, calling for accountability and warning of potential war crimes.

"Gaza is piled with rubble, piled with bodies, and piled with examples of what may be serious violations of international law," Guterres told journalists.

He also said UN-led humanitarian efforts in the devastated Palestinian enclave were being blocked or delayed and people were dying of hunger as a "result of deliberate decisions that defy basic humanity".

"Starvation of the civilian population must never be used as a method of warfare. Civilians must be protected. Humanitarian access must be unimpeded," he said. "No more excuses. No more obstacles. No more lies."

Israel has denied trying to starve Gaza, accusing Hamas of stealing aid shipments and blaming foreign aid groups for failures in delivering supplies where most needed. Both blame Israeli restrictions on aid access for spreading starvation.

With the enclave in the grips of a humanitarian crisis, the Gaza health ministry said on Thursday that four more people, including two children, had died of malnutrition and starvation in the enclave, raising the number of deaths from such causes to 317 people, including 121 children, since the war started.

Israel disputes the health ministry's fatality figures and on Wednesday asked a global hunger monitor to retract an assessment that found that Gaza City and surrounding areas are suffering from famine.

Guterres also told reporters Israel's expanded military operation in Gaza City would have "devastating consequences".

The Israeli military is preparing to seize Gaza City, the territory's largest urban centre, despite international calls on Israel to desist over fears that a ground offensive would cause significant casualties and displace the roughly one million Palestinians sheltering there.

In Gaza City, residents said families were fleeing their homes, with most heading towards the coast, as Israeli forces shelled the eastern suburbs of Shejaia, Zeitoun, and Sabra.

Israeli officials describe Gaza City as the last urban stronghold of Hamas, which ignited the war with its deadly October 2023 attack on Israel. The Islamist militant group has since been decimated by Israel's air and ground war in Gaza.

The Israeli military said in a statement that it was continuing to operate throughout the enclave targeting what it described as "terrorist organisations" and infrastructure. (Agencies)