Trapped in and around Rafah, more than 1 million Palestinians braced for Israel to complete a plan to evacuate them and launch a ground assault against Hamas fighters in the southern Gaza city.
Aid agencies warned that large numbers of civilians could die in the Israeli offensive and the UN Palestinian refugee agency said it did not know how long it could work "in such a high risk operation."
"There is a sense of growing anxiety, growing panic in Rafah," said Philippe Lazzarini, the head of the UNRWA agency. "People have no idea where to go."
Israeli Prime Minister Benjamin Netanyahu's office on Friday announced that the military was ordered to develop a plan "for evacuating the population and destroying" four Hamas battalions that it said were deployed in Rafah.
Israel cannot achieve its goal of eliminating the Hamas militants who rule Gaza while those units remain, it said.
The statement, issued two days after Netanyahu rejected a Hamas ceasefire proposal, opens new tab that included the release of hostages held by the Palestinian militants, gave no further details.
Washington, Israel's main supporter, said it would not back an assault that did not protect civilians, and had briefed Israel on a new US national security memorandum reminding countries receiving US arms to adhere to international law.
"There are no new standards in this memo. We are not imposing new standards for military aid," White House press secretary Karine Jean-Pierre told reporters. "They (the Israelis) reiterated their willingness to provide these types of assurances."
More than a million people driven southwards by more than four months of Israeli bombing of Gaza are packed into Rafah and surrounding areas on the coastal enclave's border with Egypt, which has reinforced the frontier, fearing an exodus.
Doctors and aid workers are struggling to supply even basic aid to Palestinians sheltering around Rafah.
Israeli forces have been moving southwards towards the city after first storming northern Gaza in response to the Oct. 7 rampage into southern Israel by Hamas gunmen.
The United Nations said Palestinian civilians in Rafah, opens new tab require protection, but there should be no forced mass displacement, which is barred by international law.
"No war can be allowed in a gigantic refugee camp," said Jan Egeland, secretary-general of the Norwegian Refugee Council, warning of a "bloodbath" if Israeli troops move into Rafah.
The Palestinian Presidency said Netanyahu's plans aimed to displace the Palestinian people from their land.
"Taking this step threatens security and peace in the region and the world. It crosses all red lines," said the office of Mahmoud Abbas, head of the Palestinian Authority that exerts partial self-rule in the Israeli-occupied West Bank.
An Israeli official who declined to be named said that Israel would try to organize for people in Rafah, most of whom fled there from the north, to be moved back northwards ahead of any assault.
Gaza's health ministry said at least 27,947 Palestinians had been confirmed killed in the conflict and 67,459 injured. More could be buried under rubble.
Almost one in 10 Gazans under the age of five are now acutely malnourished, according to initial UN data from arm measurements showing physical wasting.
The charity ActionAid said some Gazans were eating grass.
"Every single person in Gaza is now hungry, and people have just 1.5 to 2 litres of unsafe water per day to meet all their needs," it said.
