Israel launched its long-anticipated ground offensive in Gaza City on Tuesday, targeting Hamas militants and prompting widespread international alarm, with the UN condemning it as "carnage".
A United Nations commission accused Israel of committing "genocide" in the Palestinian territory, saying Prime Minister Benjamin Netanyahu and other senior officials had incited the crime.
The Israeli military unleashed a massive bombardment of Gaza City overnight as its troops moved deeper into the territory's largest urban hub.
"Over the past 24 hours, following extensive discussions with the political echelon, the IDF (military) has significantly expanded its operation in Gaza City," said army chief Lieutenant General Eyal Zamir.
"We are operating deep in the area, combining ground troops, precision strikes and high-quality intelligence. Our objective is to enhance the strikes on Hamas until its decisive defeat."
UN chief Antonio Guterres said Israel was "determined to go up to the end".
Israel was "not open to a serious negotiation for a ceasefire, with dramatic consequences from Israel's point of view", he said.
The military estimated there were 2,000 to 3,000 Hamas militants in central Gaza City, and that about 40 percent of residents had left and moved to the south, an army official told journalists.
An AFP journalist saw many people, including children, sleeping in front of a hospital in Gaza City after fleeing their homes.
"The people do not have money to move to the south or even to move internally," said Youssef Shanaa, who had taken refuge at the hospital.
People spoke of relentless bombing in Gaza City, much of which is already in ruins after nearly two years of Israeli strikes.
Only huge piles of rubble remained of a residential block in the north of the city hit by overnight bombing.
"Why kill children sleeping safely like that, turning them into body parts?" said Abu Abd Zaquout. "We pulled the children out in pieces."
- 'Genocide' -
The assault was "systematic ethnic cleansing targeting our people in Gaza", Hamas said in a statement.
US President Donald Trump accused Hamas of using hostages as human shields.
"I hear Hamas is trying to use the old human shield deal, and if they do that they're going to be in big trouble," he said.
Gaza's civil defence, a rescue force operating under Hamas authority, said at least 44 people had been killed by Israeli fire on Tuesday.
Media restrictions in the territory and difficulties in accessing many areas mean AFP is unable to independently verify the details provided by the civil defence or the Israeli military.
On Tuesday, the UN Independent International Commission of Inquiry (COI), which does not speak for the world body, found that "genocide is occurring in Gaza and is continuing to occur", commission chief Navi Pillay told AFP.
"The responsibility lies with the State of Israel."
The investigators said explicit statements by Israeli civilian and military authorities along with the pattern of Israeli forces' conduct "indicated that the genocidal acts were committed with intent to destroy... Palestinians in the Gaza Strip as a group".
The report concluded that Netanyahu, President Isaac Herzog and former defence minister Yoav Gallant have "incited the commission of genocide".
Israel said it "categorically rejects this distorted and false report" and called for the "immediate abolition" of the COI.
UN rights chief Volker Turk told AFP and Reuters that: "It's for the court to decide whether it's genocide or not, and we see the evidence mounting."
He also condemned the assault on Gaza City, saying it was "absolutely clear that this carnage must stop".
The European Union said the assault on Gaza City would worsen an already "catastrophic" humanitarian situation, while Britain said it would bring only "more bloodshed, kill more innocent civilians and endanger the remaining hostages".
- Statehood push -
Despite the growing criticism, US Secretary of State Marco Rubio, who visited Israel at the weekend, offered robust backing for the offensive as he met Netanyahu.
Rubio said a diplomatic solution in which Hamas demilitarises remained the US preference, although he added: "Sometimes when you're dealing with a group of savages like Hamas, that's not possible, but we hope it can happen."
Later on Tuesday, Netanyahu said he had been invited to the White House and would meet with Trump after delivering an address to the UN General Assembly later this month.
This month France is leading a UN summit in which several Western governments, angered by what they see as Israeli intransigence, plan to recognise a Palestinian state.
The October 2023 Hamas attack on Israel that sparked the war in Gaza resulted in the deaths of 1,219 people, most of them civilians, according to an AFP tally of official figures.
Israel's retaliatory campaign in Gaza has killed at least 64,964 people, also mostly civilians, according to figures from the territory's health ministry that the United Nations considers reliable.
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