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Israel's military directed the evacuation of northern Gaza, a region that is home to 1.1 million people, within 24 hours on Friday, a UN spokesman said, as Israel seeks to eradicate the Hamas militant group after its deadly attack.
The order could signal an impending ground offensive, though the Israeli military has not yet confirmed such a plan.
It said that while it was preparing, no decision has been made.
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The order, delivered to the UN, comes as Israel presses an offensive against Hamas militants.
UN spokesman Stéphane Dujarric called the order “impossible” without “devastating humanitarian consequences.”
A UN official says that the United Nation is trying to get clarity from Israeli officials at the senior most political level.
"It's completely unprecedented, the official said, speaking on condition of anonymity because he was not authorised to speak publicly.
Panicked rumours of an evacuation had begun to spread in north Gaza, home to almost half the population of the territory, in the early morning on Friday.
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A ground offensive in Gaza, which is ruled by Hamas and where the population is densely packed into a sliver of land only 40 kilometers long, would likely bring even higher casualties on both sides in brutal house-to-house fighting.
Hamas’ assault on Saturday and smaller attacks since have killed more than 1,300 people in Israel, including 247 soldiers — a toll unseen in Israel for decades — and the ensuing Israeli bombardment has killed more than 1,530 people in Gaza, according to authorities on both sides.
Israel says roughly 1,500 Hamas militants were killed inside Israel, and that hundreds of the dead in Gaza are Hamas members. Thousands have been wounded on both sides.
As Israel pounds Gaza from the air, Hamas militants have fired thousands of rockets into Israel.
Amid concerns that the fighting could spread in the region, Syrian state media reported that Israeli airstrikes on Thursday put two Syrian international airports out of service.
READ MORE: 'Enemy of civilisation': US and Israel compare Hamas to ISIS
Israeli Prime Minister Benjamin Netanyahu vowed to “crush” Hamas after the militants stormed into the country’s south on Saturday and massacred hundreds of people, including killings of children in their homes and young people at a music festival.
Amid grief and demands for vengeance among the Israeli public, the government is under intense pressure to topple Hamas rather than continuing to try to bottle it up in Gaza.
The number of people forced from their homes by Israel's airstrikes soared 25% in a day, reaching 423,000 out of a population of 2.3 million, the UN said Thursday. Most crowded into UN-run schools.
Earlier, the Israeli military pulverised the Gaza Strip with airstrikes, prepared for a possible ground invasion and said its complete siege of the territory — which has left Palestinians desperate for food, fuel and medicine — would remain in place until Hamas militants free some 150 hostages taken during their grisly weekend incursion.
READ MORE: Palestinians rush to buy food as Israel readies possible invasion
A visit by Secretary of State Antony Blinken, along with shipments of US weapons, offered a powerful green light to Israel to drive ahead with its retaliation in Gaza after Hamas' deadly attack on civilians and soldiers, even as international aid groups warned of a worsening humanitarian crisis.
Israel has halted deliveries of basic necessities and electricity to Gaza's 2.3 million people and prevented entry of supplies from Egypt.
"Not a single electricity switch will be flipped on, not a single faucet will be turned on and not a single fuel truck will enter until the Israeli hostages are returned home," Israeli Energy Minister Israel Katz said on social media.
Lt. Col. Richard Hecht, an Israeli military spokesman, told reporters Thursday that forces "are preparing for a ground manoeuvre" should political leaders order one.
