Half of Gaza's population is "starving", a senior UN official has warned as he described the humanitarian operation in the enclave as "collapsing".
Carl Skau, deputy executive director of the UN World Food Programme, said the situation inside Gaza was increasingly chaotic as people grabbed what they could from aid distribution points.
He said nine out of 10 people in Gaza - which on Saturday continued to be pounded by Israeli strikes - are not managing to eat every day.
Mr Skau said aid trucks are at risk of being stopped by desperate residents if they even slow down at an intersection.
"There is a question for how long this can continue, because the humanitarian operation is collapsing," he said.
"Half of the population are starving, nine out of 10 are not eating every day. Obviously the needs are massive."
Until now, limited quantities of aid have been delivered from Egypt through the Rafah crossing, which is ill-equipped to process large numbers of trucks.
Trucks have been driving more than 40 km (24.85 miles) south to Egypt's border with Israel before returning to Rafah, leading to bottlenecks and delays.
A new process for inspecting aid for Gaza at the Kerem Shalom crossing - on the border between Israel, Gaza and Egypt - was being tested, but efforts to get permission for trucks to enter through the crossing and ramp up relief were still ongoing, said Mr Skau.
Under the new system, trucks would come to the Kerem Shalom crossing for the first time from Jordan, before entering Gaza from Rafah, about 3km (1.86 miles) away.
But the trucks would need to be allowed to enter Gaza directly through Kerem Shalom to alleviate an increasingly desperate situation in the coastal enclave, said Mr Skau.
Israel has so far rebuffed pleas from the United Nations and others to open Kerem Shalom, but they both signalled on Thursday that the crossing could soon help process delivery of humanitarian supplies into Gaza.
"It's good, it's useful because it would also be the first time that we can then bring in a pipeline from Jordan," said Mr Skau, who visited Gaza on Friday.
Israel on Saturday ordered residents out of the centre of Gaza's main southern city Khan Younis and pounded the length of the enclave as its military operation continued.
Since a truce collapsed last week, Israel has expanded its ground campaign into the southern half of the Gaza Strip by launching the storming of Khan Younis.
Israel's Arabic-language spokesperson posted a map on X highlighting six numbered blocks of Khan Younis that residents were told to evacuate "urgently". They included parts of the city centre that had not been subject to such orders before.
Israel issued similar evacuation warnings at the start of this week before storming the eastern parts of the city.
"It might be a matter of time before they act against our area too. We have been hearing bombing all night," said Zainab Khalil, 57, displaced with 30 of her relatives and friends in Khan Younis near Jalal street where troops told people to leave.
"We don't sleep at night, we stay awake, we try to put the children to sleep and we stay up fearing the place would be bombed and we'll have to run carrying the children out. During the day begins another tragedy, and that is: how to feed the children?"
The vast majority of Gaza's 2.3 million residents have already been forced from their homes, many fleeing several times. With fighting raging across the length of the territory, residents and UN agencies say there is now effectively nowhere safe to go, though Israel disputes this.
Israel has blocked Gazans from fleeing along the main north-south route down the spine of the narrow strip, and is shunting them instead towards the Mediterranean coast.
The Palestinian health ministry said 17,700 people had been killed in Gaza since October 7, and a further 48,780 injured.
Nasser and another southern hospital, al Aqsa in Deir al-Balah, reported 133 dead and 259 wounded between them in the past 24 hours.
Amid the evacuation warning, Yemen's Houthi rebels said it will target all ships en route to Israel in the Red Sea will be targeted.
"If Gaza does not receive the food and medicine it needs, all ships in the Red Sea bound for Israeli ports, regardless of their nationality, will become a target for our armed forces," Yahya Saree said, announcing a ban on the passage of all ships en route to Israel.
Amid escalating tensions in the Red Sea, the UK has dispatched the HMS Diamond to bolster the navy's presence in the region.