Israel’s military on Friday called for all civilians of Gaza City, more than 1 million people, to relocate south within 24 hours, as it amassed tanks near the Gaza Strip ahead of an expected ground invasion.

“Now is a time for war,” Defence Minister Yoav Gallant said on Thursday as Israeli warplanes continued pounding Gaza in retaliation for the deadliest attack by Palestinian militants in its history.

The Israeli military said it would operate “significantly” in Gaza City in the coming days and civilians would only be able to return when another announcement was made.

The United Nations said it considered it impossible for such a movement to take place “without devastating humanitarian consequences.”

“The United Nations strongly appeals for any such order, if confirmed, to be rescinded avoiding what could transform what is already a tragedy into a calamitous situation,” UN spokesman Stephane Dujarric said in a statement.

Israel’s ambassador to the UN, Gilad Erdan described the UN’s response to Israel’s early warning to the residents of Gaza as “shameful”.

A Hamas official said the Gaza relation warning was “fake propaganda” and urged citizens not to fall for it.

Israel has vowed to annihilate the Hamas militant group which led the attacks on Saturday, but a ground invasion of Gaza poses serious risk with Hamas holding scores of hostages kidnapped in the assault.

Public broadcaster Kan said the Israeli death toll had risen to more than 1,300. Gaza authorities said more than 1,500 Palestinians had been killed.

Israel has put Gaza, home to 2.3 million people, under siege.

The International Committee of the Red Cross (ICRC) said fuel powering emergency generators at hospitals in Gaza could run out within hours and the United Nations World Food Programme (WFP) warned food and fresh water were running dangerously low.

“The human misery caused by this escalation is abhorrent, and I implore the sides to reduce the suffering of civilians,” ICRC regional director Fabrizio Carboni said.

‘Riddled with bullets’

Seeking to build support for its response, Israel’s government showed US Secretary of State Antony Blinken and NATO defence ministers graphic images of children and civilians they said Hamas had killed in a weekend rampage in Israel.

Blinken said they showed a baby “riddled with bullets,” soldiers beheaded and young people burned in their cars. “It’s simply depravity in the worst imaginable way,” he said. “It’s really beyond anything that we can comprehend.”

Like others across the globe, Blinken urged Israel to show restraint, but he also reiterated America’s support, saying: “We will always be there by your side.”

On Friday he was due to meet Jordan’s King Abdullah and Mahmoud Abbas, head of the Palestinian Authority in the Israeli-occupied West Bank, as part of a Middle East tour aimed at stopping spillover from the war.

Blinken also planned to visit key US allies Qatar, Saudi Arabia, Egypt and the United Arab Emirates - some with influence on Hamas, an Islamist group backed by Iran.

Israel’s military chief, Lieutenant General Herzi Halevi, said lessons would be drawn from the security failures around Gaza that enabled the attack. “We will learn, investigate, but now is the time for war,” he said.

The US military is placing no conditions on its security assistance to Israel, US Defence Secretary Lloyd Austin said, adding Washington expected Israel’s military to “do the right things” in prosecuting its war against Hamas.

Austin was due in Israel on Friday and planned to meet Israeli Prime Minister Benjamin Netanyahu.

Hamas called on Palestinians to rise up on Friday in protest at Israel’s bombardment of the enclave, urging Palestinians to march to East Jerusalem’s Al-Aqsa Mosque and clash with Israeli troops in the occupied West Bank.

Israel’s parliament approved Netanyahu’s emergency unity government late on Thursday, including a number of centrist opposition lawmakers, to display the country’s united determination to fight Hamas.

Human Rights Watch on Thursday accused Israel of using white phosphorus munitions in its military operations in Gaza and Lebanon, saying the use of such weapons puts civilians at risk of serious and long-term injury.

Israel’s military said it was “currently not aware of the use of weapons containing white phosphorus in Gaza.”

North Korea denied on Friday its weapons were used by Hamas in the attack against Israel, saying the claim made in some media reports was a bid by Washington to divert the blame for the conflict from itself to a third country.

Safety concerns prompt security measures

The US State Department will begin offering charter flights to Europe to help Americans leave Israel if they want starting Friday, the White House said.

Japan has arranged for a charter flight to depart Tel Aviv on Saturday for its citizens wishing to leave Israel, Chief Cabinet Secretary Hirokazu Matsuno told reporters on Friday.

The conflict spurred some civil unrest in Europe, with police in Paris using tear gas and water cannon to break up a banned rally in support of the Palestinian people. Some Jewish schools in Amsterdam and London were set to close temporarily due to safety concerns.

US law enforcement officials in New York and Los Angeles said they had a stepped up police presence for Friday, especially around synagogues and Jewish community centers, but some officials sought to play down the threat.

The Arab American Anti-Discrimination Committee, an Arab advocacy group, said on Thursday that FBI agents had visited mosques in different states and individual US residents with Palestinian roots, calling it a “troubling trend.” In Jerusalem, scores of Israelis gathered at the Mount Herzl military cemetery on Thursday to bury their dead.

“When you didn’t take my call, I knew you were fighting with all your power. When I realised you were missing, I could not imagine this is how it would end,” one mourner said.

In Gaza’s main southern city Khan Younis, where cemeteries were already full, dead were being buried in empty lots, like the Samour family, killed on Wednesday night in a strike that hit their house.

Palestinian rescue worker Ibrahim Hamdan drove from one bomb site to another as his team tried to pull survivors from houses destroyed by the Israeli air strikes.

“This war is harsh beyond imagining,” said Hamdan, who has worked through repeated wars since becoming a rescuer in 2007. “They knock down high-rise buildings on top of their residents.”

Gazans, mainly descendants of refugees who fled or were expelled from homes in Israel at its founding in 1948, have suffered economic collapse and repeated Israeli bombardment under a blockade since Hamas seized power there 16 years ago.

Palestinian anger has mounted in recent months, with Israel carrying out the deadliest crackdown for years in the West Bank and its right-wing government talking of seizing more land. A peace process meant to create a Palestinian state collapsed a decade ago, which Palestinian leaders say left the population with no hope, strengthening extremists.