Gaza - Israel pushed on Sunday with its brutal siege, as the focus of the deadly attacks shifted to southern Gaza where most displaced Palestinians are trapped.

US President Joe Biden stressed the "critical need" to protect civilians, in a call with Prime Minister Benjamin Netanyahu, who vowed Israel would "continue the war until all of its goals have been achieved," officials said.

As heavy fighting raged on, the Israeli army killed over 200 in 24 hours in the besieged Palestinian territory, Gazan authorities confirmed on Saturday.

The Israeli army said 153 troops had died in Gaza since it launched its ground invasion on October 27. Ten soldiers were lost in battles on Saturday, one of the deadliest days for the Israeli side.

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"This is a difficult morning, after a very difficult day of fighting in Gaza," said Netanyahu. "The war is exacting a very heavy price... but we have no choice but to keep fighting."

The army claimed soldiers had raided a northern Gaza compound near schools, a mosque, and a clinic and found "explosive belts adapted for children, dozens of mortar shells, hundreds of grenades and intelligence documents".

Hamas rejected those claims as lies meant "to justify their massacring of innocent civilians and their destructive aggression that has affected the entire infrastructure... in the already blockaded Gaza Strip."

Israel's withering military campaign, including massive aerial bombardment, has killed 20,424 people, mostly women and children, according to Gaza's health ministry.

Vast areas of Gaza lie in ruins, and its 2.4 million people have endured dire shortages of water, food, fuel, and medicine due to an Israeli siege, alleviated only by the limited arrival of aid trucks.

80% of Gazans have been displaced, according to the UN, many now shielding against the winter cold in makeshift tents and forced into the south of Gaza even as ground fighting comes closer.

Near the far southern Gaza city of Rafah, Umm Amir Abu al-Awf (27) suffered wounds to her hand and legs in a strike on her house early Sunday.

"Who won?" she said. "Nothing has been achieved except killing civilians... They keep saying Rafah is safe. It is not safe. Nowhere is safe. Every house has a martyr and injured."

Israeli military spokesperson Jonathan Conricus indicated that forces were close to gaining operational control in northern Gaza and that now "we focus our efforts against Hamas in southern Gaza."

Fighting has raged in the main southern city of Khan Yunis, the birthplace of Yahya Sinwar, Hamas' leader in Gaza and the man Israel holds most responsible for the October 7 attack.

Elsewhere, Palestinian rescuers scrambled again to pull survivors and bodies from the rubble of a destroyed residential building, after a strike hit in the central city of Deir al-Balah.

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"I was praying when a huge explosion occurred," said Yazan Moqbel, a wounded man whose sister was still under the broken concrete. "Rubble fell on us. I didn't know what happened."

The head of the UN refugee agency, Filippo Grandi, urged an end to the suffering in the third month of Israel's brutal campaign.

"For aid to reach people in need, hostages to be released, more displacement to be avoided and above all stop the appalling loss of lives, a humanitarian ceasefire in Gaza is the only way forward," he wrote on X, formerly Twitter.

"War defies logic and humanity, and prepares a future of more hatred and less peace."

On Friday, the United States allowed the passage of a UN Security Council resolution that effectively called on Israel to allow "immediate, safe and unhindered" deliveries of life-saving aid to Gaza "at scale."

World powers had wrangled for days over the wording and, at Washington's insistence, toned down some provisions – including removing a call for a ceasefire.

One displaced Gazan, Ahmad al-Burawi, now living in Rafah in southern Gaza, said: "We just want to return to our lands, that's all. We want a solution... People are dying."

As the war rages on, Christians around the world celebrate Christmas Eve, and festivities are usually held in the occupied West Bank city of Bethlehem where they believe Jesus was born.

But this year, the city is almost deserted, with few worshippers around and no Christmas tree erected, after church leaders decided to forego "any unnecessarily festive" celebrations, in solidarity with Gazans.

Palestinian president Mahmoud Abbas voiced hope Christmas would mark "a cessation of the Israeli war against the Palestinian people in Gaza, as well as across the occupied Palestinian territories."

The Gaza massacre has heightened tensions across the Middle East, where US-backed Israel faces widespread opposition, including from groups in Lebanon, Syria, Iraq, and Yemen that have voiced strong support for Palestinians.

Cross-border fire has erupted almost daily between Israel and Lebanon's Hezbollah movement.

And Yemen's Houthis have fired at cargo vessels in the Red Sea, leading the United States to build a naval task force to deter the missile and drone strikes.

The US military said four drones had targeted the USS Laboon, but had been shot down, and that an Indian-flagged tanker was hit and sent out a distress call.

Iran's deputy foreign minister, Ali Bagheri, denied US accusations that his country was orchestrating the campaign, saying the Houthis act on their "own decisions and capabilities."