Israel on Saturday hit parts of Gaza including Rafah where it expanded an evacuation order, as the UN warned an outright invasion of the crowded city risked an "epic" disaster.
AFP journalists, medics and witnesses reported strikes across the coastal territory, where the UN says humanitarian relief is blocked after Israeli troops defied international opposition and entered eastern Rafah this week.
That effectively shut a key aid crossing and suspending traffic through another.
At least 21 people were killed during strikes in central Gaza and taken to Al-Aqsa Martyrs Hospital in Deir al-Balah city, a hospital statement said.
Bodies covered in white dust lay on the ground in a courtyard of the facility. A man in a baseball cap leaned over one body bag, clasping a dust-covered hand that protruded.
The feet of another corpse poked from under a blanket bearing the picture of a large teddy bear.
In Rafah, witnesses reported intense air strikes near the crossing with Egypt, and AFP images showed smoke rising over the city.
Other strikes occurred in north Gaza, witnesses said.
Hamas on Saturday accused Israel of "expanding the incursion into Rafah to include new areas in the centre and the west of the city".
Israeli troops on Tuesday seized and closed the Palestinian side of the Rafah crossing -- through which all fuel passes into Gaza -- after ordering residents of eastern Rafah to evacuate.
The army said Saturday troops were fighting "armed terrorists" at the crossing and had found "numerous underground tunnel shafts".
The war began with Hamas's unprecedented 7 October attack on Israel, which resulted in the deaths of more than 1,170 people, mostly civilians, according to an AFP tally of Israeli official figures.
During their attack, militants also seized hostages. Israel estimates 128 of them remain in Gaza including 36 who the military says are dead.
Israel's retaliatory offensive has killed at least 34,971 people in Gaza, mostly women and children, according to the Hamas-run territory's health ministry.
While mediation efforts towards a truce and hostage release appeared to stall, Hamas's armed wing said a hostage who appeared in a video it released earlier on Saturday had died from wounds suffered in an Israeli strike.
The Ezzedine Al-Qassam Brigades said Nadav Popplewell, a British-Israeli man, had been wounded in a strike a month ago and died "because he did not receive intensive medical care because the enemy has destroyed the Gaza Strip's hospitals".
The Israeli military did not offer any comment on the earlier video and AFP was unable to independently verify its authenticity.
US President Joe Biden on Saturday said a ceasefire would be achieved "tomorrow" if Hamas released the hostages.
The new evacuation order for eastern Rafah, posted on X by Israeli military spokesman Avichay Adraee, said the designated areas had "witnessed Hamas terrorist activities in recent days and weeks".
Military spokesman Daniel Hagari later said "we have eliminated dozens of terrorists in eastern Rafah".
Israel on Saturday said 300,000 people had fled Rafah since an initial evacuation order, as more residents piled water tanks, mattresses and other belongings onto vehicles and prepared to flee again.
"We don't know where to go," said Farid Abu Eida, who was preparing to leave Rafah, having already been displaced there from Gaza City.
"There is no place left in Gaza that is safe or not overcrowded... There's nowhere we can go."
Journalists as well began dismantling their tents and packing their equipment to leave the city.
"Where to? After Rafah there is expulsion, not displacement. This is the question that Palestinians ask, what next?" said journalist Nabil Diab.
The evacuation order on Saturday told residents to go to the "humanitarian zone" of Al-Mawasi, on the coast northwest of Rafah.
That area has "extremely limited access to clean drinking water, latrines" and other basic services, said Sylvain Groulx, Doctors Without Borders (MSF) emergency coordinator in Gaza.
EU chief Charles Michel said on social media that Rafah civilians were being ordered to "unsafe zones", denouncing it as "unacceptable".