Severely malnourished children in the Gaza Strip will be "certainly condemned to death" unless aid gets to them quickly, UNRWA chief Philippe Lazzarini warned on Thursday.
The head of the UN agency for Palestinian refugees said hunger was particularly acute in the north — where Gaza City is — where an estimated one million people remain.
Lazzarini said an evaluation on how famine has evolved in the Gaza Strip was due to be published soon, adding UNRWA health centres had seen a six-fold increase in the number of severely malnourished children since March.
"If no measures are taken immediately, they are certainly condemned to death," he told the Geneva Press Club.
People in the Palestinian territory are already dying of hunger and "there will be more, there's no doubt about it", said Lazzarini.
Rights group Amnesty International earlier this week accused Israel of enacting a "deliberate policy" of starvation in Gaza.
Without naming Israel, Lazzarini labelled it a "manufactured famine" and said food had been used "as a weapon of war".
Israel heavily restricts aid coming into Gaza but has repeatedly rejected claims of deliberate starvation.
Israel has announced a plan to take over Gaza City and has warned that the north of the territory will be evacuated.
The UNRWA commissioner-general warned that a weakened, hungry population would struggle to withstand a new military operation in the city.
"We had described hell on Earth in Gaza," he said.
"If this scenario were to unfold, even if we talk about the evacuation of people from Gaza to the south, many will no longer even have the strength to move."
Israeli Prime Minister Benjamin Netanyahu was expected to give final approval on Thursday for plans to take over Gaza City, an operation that could start within days. The widening of the 22-month offensive against Hamas appears to be proceeding despite protests in both Israel and the Palestinian enclave.
Netanyahu was set to meet with top security officials to sign off on the plans, according to an Israeli official who was not authorized to brief media and spoke on condition of anonymity. It was unclear whether they would discuss a ceasefire proposal from Arab mediators that Hamas says it has accepted.
The Israeli military began calling medical officials and international organizations in the northern Gaza Strip to encourage them to evacuate to the south ahead of the expanded operation. The military plans to call up 60,000 reservists and extend the service of 20,000 more.
Israeli strikes meanwhile killed at least 36 Palestinians across Gaza on Thursday, according to local hospitals. A renewed offensive could bring even more casualties and displacement to the territory, where the war has already killed tens of thousands and where experts of have warned of imminent famine.
Many Israelis fear it could also doom the remaining 20 or so living hostages taken by Hamas-led militants in the Oct. 7, 2023, attack that ignited the war.
Israeli troops have already begun more limited operations in the city's Zeitoun neighborhood and the built-up Jabaliya refugee camp, areas where they have carried out several previous major operations over the course of the war, only to see militants later regroup.
The military says it plans to operate in areas where ground troops have not yet entered and where it says Hamas still has military and governing capabilities.
So far, there has been little sign of Palestinians fleeing en masse, as they did when Israel carried out an earlier offensive in Gaza City in the opening weeks of the war. The military says it controls around 75% of Gaza and residents say nowhere in the territory feels safe.
Hundreds gathered for a rare protest in Gaza City on Thursday against the war and Israel's plans to support the mass relocation Palestinians to other countries.
Women and children held placards reading "Save Gaza" and "Stop the war, stop the savage attack, save us," against a backdrop of destroyed buildings as Palestinian music played. Unlike in previous protests, there were no expressions of opposition to Hamas.
"We want the war on Gaza to stop. We don't want to migrate. Twenty-two months ... it's enough. Enough death. Enough destruction," said Bisan Ghazal, a woman displaced from Gaza City.
Agencies