Hamas has called on Palestinians to stay in their homes after Israel issued sweeping evacuation orders in Gaza.

The Hamas Authority for Refugee Affairs called on residents of the north of the territory to “remain steadfast in your homes and to stand firm in the face of this disgusting psychological war waged by the occupation”.

Israel has ordered the evacuation of northern Gaza, including Gaza City, which is home to hundreds of thousands of people.

Gaza air strike
Palestinians look for survivors after an Israeli air strike in Rafah refugee camp, southern Gaza Strip, on Thursday (AP)

Palestinians would only be able to flee south within Gaza as Israel has completely sealed off the territory, a narrow strip of land about 25 miles long.

Later on Friday, Hamas said Israel’s heavy bombardment of the Gaza Strip killed 13 hostages, including foreigners, held by the group.

Hamas’ military wing said the 13 were killed in various locations over the past 24 hours.

Destroyed Israeli tank
Palestinians wave their national flag and celebrate by a destroyed Israeli tank at the southern Gaza Strip fence east of Khan Younis (AP)

It did not give the nationality of the foreigners, and there has been no confirmation over the claims from Israel.

The Israeli military had said it would operate with “significant force” in Gaza in the coming days and is calling on civilians to evacuate.

Spokesman Jonathan Conricus said Israeli forces “will make extensive efforts to avoid harming civilians”.

He added: “Out of an understanding that there are civilians here who are not our enemy and we do not want to target them, we are asking them to evacuate.”

The directive came on the heels of what the United Nations said was a warning they received from Israel to evacuate 1.1 million people living in northern Gaza within 24 hours.

Suffering in Gaza has risen dramatically with Palestinians desperate for food, fuel and medicine, while the territory’s only power plant shut down for lack of fuel. The mortuary at Gaza’s biggest hospital overflowed as bodies came in faster than relatives could claim them.

US defence secretary Lloyd Austin is set to visit on Friday, a day after American secretary of state Antony Blinken was in Israel for talks with Prime Minister Benjamin Netanyahu.

The war has claimed at least 2,800 lives on both sides since Hamas launched an incursion on October 7.

A pro-Palestinian protester in Madrid
A woman with a Palestinian flag painted on her face, cries during a protest against Israeli air strikes on Gaza in Madrid (AP)

Inas Hamdan, an officer at the UN Palestinian refugee agency in Gaza City, said: “This is chaos, no-one understands what to do.”

She said all the UN staff in Gaza City and northern Gaza had been told to evacuate south to Rafah.

Nebal Farsakh, a spokesperson for the Palestinian Red Crescent in Gaza City, claimed there was no way more than one million people could be safely moved within the timeframe specified, saying: “Forget about food, forget about electricity, forget about fuel. The only concern now is just if … you’re going to live.”

She added: “What will happen to our patients?

“We have wounded, we have elderly, we have children who are in hospitals.”

The flurry of directives was taken as signalling an expected Israeli ground offensive, though the Israeli military has not yet confirmed such a decision. On Thursday it said that while it was preparing, no decision has been made.

The UN said the broad evacuation warning it received for all of Gaza’s north also applies to all UN staff and to the hundreds of thousands who have taken shelter in UN schools and other facilities since Israel launched round-the-clock air strikes on Saturday.

“The United Nations considers it impossible for such a movement to take place without devastating humanitarian consequences,” UN spokesman Stephane Dujarric said.

“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.”

Another UN official said that the UN is seeking clarity from Israeli officials at the most senior political level.

A ground offensive in Gaza, which is ruled by Hamas, would likely bring even higher casualties on both sides in brutal house-to-house fighting.

Hamas’ unprecedented assault last 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.

Gaza casualty is rescued
Palestinians evacuate wounded people after an Israeli air strike in Rafah refugee camp, southern Gaza (AP)

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 air strikes on Thursday put two Syrian international airports out of service.

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 children in their own 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 air strikes soared by 25% in a day, reaching 423,000 out of a population of 2.3 million, the UN said on Thursday.

On Thursday, the Israeli military pulverised the Gaza Strip with air strikes, prepared for a possible ground invasion and said its complete siege of the territory would remain in place until Hamas militants free some 150 hostages taken during their grisly weekend incursion.