Israeli forces were encircling southern Gaza's main city on Wednesday, battling Hamas militants through streets and buildings in some of the most intense combat of the two-month war.
The focus of the conflict has shifted to the besieged territory's south following fierce fighting and bombardment that reduced much of the north to rubble and forced nearly two million people to flee their homes.
Israeli tanks, armoured personnel carriers and bulldozers were seen on Tuesday near southern Gaza's city of Khan Yunis, forcing already displaced civilians to pack up and flee again, witnesses told AFP.
"Our forces are now encircling the Khan Yunis area in the southern Gaza Strip," Israel's army chief Herzi Halevi said late Tuesday.
"We have secured many Hamas strongholds in the northern Gaza Strip, and now we are operating against its strongholds in the south."
The fighting on Tuesday was "the most intense day since the beginning of the ground operation" in late October, the army's Southern Command chief Major General Yaron Finkelman said.
Israel declared war on Hamas after the militant group's October 7 attacks that killed 1,200 people, mostly civilians, according to Israeli authorities, and saw around 240 hostages taken.
The latest toll from the Hamas-run government media office said 16,248 people in Gaza, most of them women and children, had been killed.
Israel has vowed to destroy Hamas and free 138 hostages still held after scores were freed during a short-lived truce.
Several Hamas commanders were killed in an air strike near the Indonesia Hospital, the Israeli military said early Wednesday on X.
The Hamas-run health ministry said 25 people had died in a strike on Tuesday that hit a school where displaced people were sheltering.
Ambulances, trucks and other vehicles delivered bloodied, dust-covered people to Khan Yunis's Nasser hospital, including children.
"My cousin called me and told me to come because my sister's body was lying in a schoolyard," resident Mohammed Saloul told AFP.
- 'Nowhere is safe' -
Israel had previously told civilians in the north of the densely populated Gaza Strip to seek shelter in the south of the territory, with many fleeing to Khan Yunis believing it would be safer.
As the war expands, Israel has told people to move even further south, sparking "panic, fear and anxiety", according to Philippe Lazzarini, head of the UN agency for Palestinian refugees, UNRWA.
People were being pushed into an area that is less than one-third of the Gaza Strip, with roads to the south clogged, he said.
International aid groups have condemned the succession of orders to flee from one area to another, saying that civilians were running out of options.
"Nowhere is safe in Gaza," said United Nations humanitarian chief Martin Griffiths.
"Not hospital, not shelters, not refugee camps. No one is safe."
Following demands to create areas where civilians could shelter, Israel's army published a map it said was intended to enable Gazans to "evacuate from specific places for their safety if required".
But the UN criticised the map on Tuesday, saying it was impossible to create safe zones for civilians to flee to inside Gaza.
"The so-called safe zones... are not scientific, they are not rational, they are not possible, and I think the authorities are aware of this," said James Elder, spokesman for the UN children's agency UNICEF.
The violence in Gaza "now ranks amongst the worst assaults on any civilian population in our time and age", according to the Norwegian Refugee Council, which also warned of the dire public health consequences of the approaching winter.
Their belongings piled onto donkey carts, battered vehicles and camels, Gazans headed south to try to escape the expanding Israeli offensive.
An estimated 1.9 million people are displaced in Gaza -- roughly three-quarters of the population, according to UN figures.
In northern Gaza, the Israeli military said it had encircled the Jabalia refugee camp and also raided a Hamas Internal Security Forces command and control centre.
It said the number of Israeli soldiers killed since the war began had risen to 82.
- 'Shameful' -
US President Joe Biden called for the condemnation of "sexual violence" committed by Hamas, after allegations of rape during the October 7 attacks, which the militant group denies.
Biden's comments come after campaigners in Israel have criticised what they see as a muted international response to violence against women during the attack.
The United States, Israel's most important ally, has also ramped up calls for greater efforts to prevent civilian deaths in Gaza.
US aid chief Samantha Power announced $21 million in new assistance for Gazans during a visit to neighbouring Egypt, including for hygiene, shelter and food supplies.
Israel said this week it was not seeking to force Palestinian civilians to permanently leave their homes in the Gaza Strip, and was asking aid groups to help provide shelter in the tiny coastal area of Al-Mawasi.
Fighting in Gaza resumed after the collapse on Friday of a Qatar-mediated truce that saw scores of Israeli and other hostages released in exchange for Palestinian prisoners.
Qatar's ruler, Sheikh Tamim bin Hamad Al-Thani, said his country was "constantly working to renew" the truce and denounced what he called "shameful" international inaction over the war.
The war has sparked fears of a wider regional conflict, with frequent exchanges of fire with Iran-backed Hezbollah across Israel's border with Lebanon.
A Lebanese soldier was killed by Israeli fire on a military post near the country's southern border Tuesday, the army said.
Israel's army acknowledged the incident, saying in a post on X that it had targeted a Hezbollah position in an effort "to eliminate an imminent threat".
The occupied West Bank has also seen a surge in violence.
The killing of a 25-year-old, Mohammed Youssef Manasra, in an Israeli raid on Qalandia refugee camp added to more than 250 Palestinians killed in the West Bank since October, according to Palestinian authorities.