Over 200 people were killed in Israeli strikes on Gaza in the last 24 hours, according to the Hamas-run health ministry.
It said that the toll of the Palestinians killed in the war so far has now climbed to 21,320 - nearly 1% of Gaza's population. Thousands more dead are feared to be buried or lost in the ruins.
Israeli tanks have advanced deep into a town in central Gaza after days of relentless bombardment that forced tens of thousands of already displaced Palestinian families to flee in a new exodus.
A Palestinian journalist posted pictures of Israeli tanks near a mosque in a built-up area of Bureij, the armoured contingent having apparently advanced from orchards on the eastern outskirts.
Further south, Israeli forces struck the area around a hospital in the heart of Khan Younis, Gaza's main southern city, where residents feared a new ground push into territory crowded with families made homeless in 12 weeks of war.
Israel has escalated its ground offensive in Gaza sharply since just before Christmas despite public pleas from its closest ally the US to scale the campaign down in the closing weeks of the year.
It launched the war to destroy the militant Islamist Hamas movement that runs Gaza after fighters rampaged through Israeli towns in a cross-border raid on 7 October, killing 1,200 people and taking about 240 hostages.
Of the hostages, 110 were freed during a short truce in late November and another 23 have now been declared dead in absentia, an Israeli government spokesperson said.
The main focus of fighting is now in central areas south of the wetlands that bisect the narrow coastal strip, where Israeli forces have ordered civilians out over the past several days as their tanks close in.
Tens of thousands of people fleeing the densely packed Nusseirat, Bureij and Maghazi districts were heading south or west into the already overwhelmed city of Deiral-Balah along the Mediterranean coast, crowding into hastily built camps of makeshift tents.
"Over 150,000 people - young children, women carrying babies, people with disabilities and the elderly - have nowhere to go," the main UN organisation operating in Gaza, UNRWA, said in a social media post.
The eastern part of Bureij was a theatre of heavy fighting this morning, with Israeli tanks thrusting in from the north and east, residents and militants said.
"That moment has come, I wished it would never happen, but it seems displacement is a must," said one 60-year-old man who had been forced to move with at least 35 family members.
"We are now in a tent in Deir al-Balah because of this brutal Israeli war," he told Reuters by phone.
Fighting near hospital in Khan Younis
Khan Younis, where Israeli forces advanced this month after a truce collapsed on 1 December, also came under heavy bombardment this morning from warplanes and tanks near the al-Amal hospital, west of Israeli positions.
The Palestinian Red Crescent, which runs the hospital and has its headquarters nearby, said ten Palestinians were killed and 12 wounded in one bombardment there, the third strike targeting the area around the hospital in less than an hour.
Residents said they believed Israeli forces were trying to provoke a new exodus ahead of a further ground assault.
Nearby at Nasser Hospital, the main medical centre in Khan Younis and largest still functioning in Gaza, women and children shrieked as the dead and wounded were brought in.
Israel reported three more of its soldiers killed, bringing its toll in the ground campaign to 169. The past week has seen some of its heaviest losses of the war so far.
Virtually all of Gaza's 2.3 million residents have been driven from their homes at least once and many have been forced to flee several times. Only a handful of hospitals still function.
In a statement, the Israeli military said it "regrets the harm caused to uninvolved civilians" from a 24 December air strike on the Maghazi refugee camp that killed 70 people, according to the Palestinian health ministry.
The military statement said warplanes struck two targets "adjacent" to where Hamas militants were operating, and a preliminary inquiry showed that further buildings nearby were also hit, "which likely caused unintended harm to additional uninvolved civilians".
"The IDF ... is acting to draw conclusions and learn lessons from this event," it added.
The Palestinian health ministry denounced the attack as a massacre in a crowded residential square.
Over the course of the war, the Israeli military has expressed regret for civilian deaths but it blames Hamas for operating in densely populated areas or using civilians as human shields, a charge the group denies.
US President Joe Biden warned earlier this month that "indiscriminate bombing" in Gaza jeopardised sympathy for Israel among its allies.
Washington has said Israel should make a transition from full-scale ground war to a targeted campaign against Hamas leaders.
Egypt, which has acted as a mediator including hosting the leader of Hamas last week, said it had put forward a proposal to end the bloodshed, including a three-stage plan for a ceasefire, but had yet to hear the warring sides' responses.
Israel says it will not halt its ground campaign until it annihilates Hamas, describing this as its only option to safeguard its security and free remaining hostages.
Palestinians say wiping out Hamas is an unachievable aim given the militant group's diffuse structure and deep roots in a territory it has ruled since 2007.
UN urges Israel to end 'unlawful killings' in West Bank
A United Nations report issued today said the human rights situation in the occupied West Bank was rapidly deteriorating and urged Israel to "end unlawful killings" against the Palestinian population.
"The use of military tactics and weapons in law enforcement contexts, the use of unnecessary or disproportionate force, and the enforcement of broad, arbitrary and discriminatory movement restrictions that affect Palestinians are extremely troubling," UN rights chief Volker Turk said in a statement.
