JERUSALEM (AP) — Israel’s military told some one million Palestinians on Friday to evacuate northern Gaza and head to the southern part of the besieged territory, an unprecedented order applying to almost half the population ahead of an expected ground invasion against the ruling Hamas militant group.

The United Nations (UN) warned that so many people fleeing en masse — with just a 24-hour deadline — would be calamitous. Hamas, which staged a shocking and brutal attack on Israel nearly a week ago and has fired thousands of rockets since, dismissed it as a ploy and called on people to stay in their homes.

The evacuation order, which includes Gaza City, home to hundreds of thousands of Palestinians, sparked widespread panic among civilians and aid workers already running from Israeli airstrikes and contending with a total siege and a territory-wide blackout.

“Forget about food, forget about electricity, forget about fuel. The only concern now is just if you’ll make it, if you’re going to live,” said Nebal Farsakh, a spokesperson for the Palestinian Red Crescent in Gaza City, as she broke into heaving sobs.

The war has already claimed over 2,800 lives on both sides and sent tensions soaring across the region. Israel has traded fire in recent days with Lebanon’s Hezbollah militant group, sparking fears of an ever-wider conflict, though that frontier is currently calm.

Weekly Muslim prayers brought protests across the Middle East, and tensions ran high in Jerusalem’s Old City. The Islamic endowment that manages a flashpoint holy site in the city, the Al-Aqsa Mosque compound, said Israeli authorities barred all Palestinian men under the age of 50 from entering.

Israel has bombarded Gaza round-the-clock since a weekend attack in which Hamas fighters stormed into the country’s south and massacred hundreds, including children in their homes and young people at a music festival. Militants also snatched some 150 people and dragged them into Gaza.

Hamas said Israel’s airstrikes killed 13 of the hostages in the past day. It said the dead included foreigners but did not give their nationalities.

Israeli military spokesperson Rear Adm. Daniel Hagari denied that, telling Al-Jazeera Arabic that “we have our own information and do not believe the lies of Hamas.”

Israel said Thursday it would allow no supplies into Gaza until Hamas frees the hostages.

The military urged civilians in Gaza’s north to move south — an order that the UN said affects 1.1 million people. If carried out, that would mean the territory’s entire population cramming into roughly the southern half of the strip, which is only 40 kilometres (25 miles) long, even as Israeli strikes continued Friday to hammer neighbourhoods across southern Gaza.

Israel said it needed to target Hamas’ military infrastructure, much of which is buried deep underground. Another spokesperson, Jonathan Conricus, said the military would take “extensive efforts to avoid harming civilians” and that residents would be allowed to return when the war is over.

Hamas militants operate in civilian areas, where Israel has long accused them of using Palestinians as human shields. A mass evacuation of civilians, if carried out, would leave their fighters exposed as never before.

“The camouflage of the terrorists is the civil population,” Israeli Defense Minister Yoav Gallant said at a news conference with US Defence Secretary Lloyd Austin. “Therefore, we need to separate them. So those who want to save their life, please go south.”

But UN spokesperson Stephane Dujarric said it would be impossible to stage such an evacuation without “devastating humanitarian consequences.” He called on Israel to rescind any such orders, saying they could “transform what is already a tragedy into a calamitous situation.”

Hamas, meanwhile, called on Palestinians to stay in their homes, saying Israel “is trying to create confusion among citizens and harm the cohesion of our internal front.” It urged Palestinians to ignore what it said was ”psychological warfare.”