The UN described the immediate movement of some 1.1 million people -- nearly half of the 2.4 million in the Gaza Strip -- "impossible".
Thousands of Palestinians fled to southern Gaza in search of refuge Friday after Israel warned them to evacuate before an expected ground offensive against Hamas in retaliation for the deadliest attack in Israel's history.
The call to get out came six days after Hamas gunmen burst through the heavily militarised border around the Gaza Strip and killed more than 1,300 people -- most of them civilians -- in an attack compared to 9/11 in the United States.
Nearly 1,800 Gazans -- again most of them civilians and including over 580 children -- have been killed in waves of missile strikes on the densely populated enclave, the health ministry said.
Hamas, proscribed as a terrorist organisation by the European Union and the United States, took an estimated 150 Israeli, foreign and dual national hostages back to Gaza during its initial attack, according to Israel.
The militant group said on Friday that 13 of them had been killed in Israeli air strikes. It has previously said four hostages died in bombardments.
Germany Foreign Minister Annalena Baerbock, visiting Israel on Friday, said Hamas was using residents as a "shield".
Tensions meanwhile rose across the Middle East and beyond, with angry protests in support of the Palestinians, while Israel faced the threat of a separate confrontation with Hezbollah in Lebanon.
People attend a rally in support of Palestinians in the Gaza Strip at Bayfront Park in Miami, Florida, US on October 13, 2023. PHOTO | AFP
In the occupied West Bank, at least nine Palestinians were killed by Israeli fire during protests supporting Gaza, taking the toll there to 44 since Saturday, the health ministry said.
At a news conference in Ramallah, Palestinian Prime Minister Mohammed Shtayyeh accused Israel of committing "genocide" in Gaza.
But Israeli Prime Minister Benjamin Netanyahu's spokeswoman Tal Heinrich told AFP: "Everything that happens in Gaza is Hamas's responsibility."
In Gaza, UN officials said the Israeli military, whose troops are massing at the border, had told them the evacuation should be carried out "within the next 24 hours".
It later admitted it would take more time, however, and did not confirm it had set the deadline.
But the United Nations described the immediate movement of some 1.1 million people -- nearly half of the 2.4 million in the Gaza Strip -- "impossible".
It urgently appealed for the order to be rescinded. Aid agencies have warned mass evacuations would stretch support to the limit, as fuel, food and water dwindled due to an Israeli blockade.
Hospitals are struggling to cope with the dead and wounded from the relentless bombardment, and the health system was already "at a breaking point", the World Health Organisation said.
Ashraf al-Qudra, from the Gaza Health Ministry, said hospitals were "starting to lose capacity" and medicine was running out.
In Jordan, after a meeting with visiting US Secretary of State Antony Blinken, King Abdullah II called for "humanitarian corridors" to be opened urgently.
Egypt, which runs the Rafah crossing to the south of Gaza, faces a dilemma of accepting refugees with the possibility that Israel may never let them return, weakening Palestinian aspirations for statehood.
"Where to go?" asked Umm Hossam, 29, who was among the thousands fleeing.
"How long will the strikes and death last? We have no homes left, every area of Gaza is under threat," she added, her face streaked with tears.
AFP correspondents in Gaza said the Israeli military on Friday dropped flyers warning residents to flee "immediately" south of Wadi Gaza, with a map pointing south across a line in the centre of the 40 kilometre-long (25 mile-long) territory.
The army said it "will continue to operate significantly in Gaza City and make extensive efforts to avoid harming civilians".
"Hamas terrorists are hiding in Gaza City inside tunnels underneath houses and inside buildings populated with innocent civilians."
AFP correspondents said there were "heavy strikes" in the northern Gaza Strip on Friday morning, including Al-Shati refugee camp and Gaza City, primarily targeting residential buildings.
The Hamas media office also reported Israeli air raids on Khan Yunis and Rafah in the south.
The Israeli military said its "fighter jets struck 750 military targets in the northern Gaza Strip overnight" including "residences of senior terrorist operatives used as military command centres".
A fireball erupts from an Israeli airstrike in Gaza City on October 12, 2023. PHOTO | AFP
Netanyahu, who was in security talks at military headquarters on Friday, has vowed to "crush" Hamas, and has likened the group to the so-called Islamic State.
But in Geneva, the International Committee of the Red Cross said the unjustifiable "horrific" attacks on Israel could equally not justify "the limitless destruction of Gaza".
Israel also denied claims from rights group that it has used the incendiary weapon white phosphorus, which can cause serious burns if it hits people.
Hamas has said Palestinians rejected the evacuation request, yet thousands of Gazans were on the move in search of safety, carrying plastic bags of belongings, suitcases on their shoulders and children in their arms.
Some walked while others drove, with belongings strapped high to the roofs of their trucks, cars and carts pulled by donkeys.
More than 423,000 people have already fled their homes, according to the UN, which said the evacuation order could turn what is "already a tragedy into a calamitous situation".
Gaza has been under a land, air and sea blockade since 2006 and Israel has vowed not to turn back on water, food and power supplies until all hostages are freed.
Norway's Foreign Minister Anniken Huitfeldt condemned the siege while Arab League chief Ahmed Abul Gheit said Israel's evacuation order is a "forced transfer" that constitutes "a crime".
Palestinian President Mahmud Abbas said it will be "tantamount to a second Nakba" or "catastrophe", referring to the 760,000 Palestinians who fled or were expelled from their homes during the 1948 war that accompanied Israel's creation.
Israel has called up 300,000 reservists while forces, tanks and heavy weapons have been moved to the southern desert area around Gaza, an AFP correspondent reported.
In fields along the border, artillery fires like clockwork with a deafening noise every 30 seconds towards barely visible targets in Gaza, shaking the earth.
But any ground offensive is complicated by the presence of hostages, whom Hamas has threatened to kill one by one if bombardments are carried out without warning.
Israeli soldiers have swept the southern towns and kibbutz farming communities since Saturday.
They said they found the bodies of 1,500 militants, as well as large numbers of civilians killed by Hamas fighters.
Yossi Landau, who has 33 years' volunteer experience with Zaka, which recovers the bodies of people who suffered unnatural deaths, said in Beeri, just east of Gaza, he found a dead woman with her stomach "ripped open, a baby was there, still connected with the cord, and stabbed".
They were among more than 100 people killed in Beeri, while around 270 were gunned down or burned in their cars at the nearby Supernova music festival.
Hamas has denied that its fighters killed infants.
Israel faces a potential second front in the north after the Iran-backed Hezbollah group in Lebanon said it was "fully prepared" to join Hamas in the war when the time was right.
There has been cross-border fire in recent days, sparking concern about regional stability and prompting the United States to send additional munitions and its largest aircraft carrier.
US President Joe Biden has warned other regional powers not to get involved. Pentagon chief Lloyd Austin told Israel Friday US support was "iron-clad".
Israel's arch foe Iran has long financially and militarily backed Hamas and praised its attack, but insists it was not involved.