After 18 months of war, the situation in Gaza "is probably the worst" it has been, the UN's humanitarian office has said, with the head of the world body's Palestinian refugee agency decrying the aid stoppage on Friday as "politically motivated starvation".

WFP, one of the main providers of food assistance in the Palestinian territory, said it had "delivered its last remaining food stocks to hot meals kitchens in the Gaza Strip" on Friday. It said "these kitchens are expected to fully run out of food in the coming days".

Philippe Lazzarini, head of the UN Palestinian refugee agency UNRWA, said the crisis was "manmade".

"The Government of Israel continues to block the entry of food + other basics," he wrote on X. "Nearly 2 months of siege. Calls to bring in supplies are going unheeded." 

The World Health Organization (WHO) said the situation was no different for medical supplies.

After blocking aid during an impasse over the future of a ceasefire with Hamas, Israel resumed its bombardment of Gaza on March 18, followed by a ground offensive.

Mohammed al-Mughayyir, an official with Gaza's civil defence rescue agency, told AFP that the death toll from Israeli strikes on Friday had risen to at least 40. 

In the evening, the Israeli military issued an evacuation order for Palestinians in Zeitun and two nearby areas in the territory's north ahead of another planned strike, saying it was responding to "terrorist activity" and "operating with force".

Gazans say they are threatened with death not just from bombardment, but from a lack of food.

"We are literally dying of hunger," Tasnim Abu Matar, a Gaza City resident, said earlier this week.

"For weeks, hot meal kitchens have been the only consistent source of food assistance for people in Gaza. Despite reaching just half the population with only 25 percent of daily food needs, they have provided a critical lifeline," the WFP said.

The agency added that "more than 116,000 metric tons of food assistance, enough to feed one million people for up to four months" was positioned at aid corridors ready to be brought in "as soon as borders reopen".

Following WFP's warning, the WHO chief said medical supplies were also "running out" in Gaza while 16 WHO trucks wait to enter.  

"This aid blockade must end. Lives depend on it", Tedros Adhanom Ghebreyesus said on X.

WFP added that all 25 bakeries it supports in Gaza were forced to close on March 31 as wheat flour and cooking oil ran out during "the longest closure the Gaza Strip has ever faced".

Israeli Defence Minister Israel Katz last week said his country would continue blocking aid because the tactic is "one of the main pressure levers preventing Hamas from using [aid] as a tool with the population".

On Wednesday, Germany, France and Britain called for an end to the "intolerable" blockade and warned of "an acute risk of starvation, epidemic disease and death".

The International Criminal Court in November issued an arrest warrant for Israeli Prime Minister Benjamin Netanyahu partly on suspicion of the war crime of starvation as a method of warfare. Netanyahu rejected the accusations as "absurd and false".

At least 2,062 people have been killed in Gaza since Israel resumed its campaign against Hamas militants in mid-March. That brings the overall death toll of the war to 51,439, most of them civilians, according to the territory's health ministry.

Hamas's October 2023 attack on Israel that began the war resulted in the deaths of 1,218 people, mostly civilians, according to an AFP count based on official Israeli figures.