Gallant, the defence minister, said: “We will wipe this thing called Hamas, Isis-Gaza, off the face of the Earth. It will cease to exist”.

Gantz, a former general, said it was a time to join together and win. “There is a time for peace and a time for war. Now is a time for war,” he said.

Saturday’s surprise attack – the worst in Israel’s 75-year history – has seen a total of 1,200 people killed in the Islamist militants’ onslaught, according to Israeli forces. Most were civilians.

In Gaza, officials reported more than 1,200 people killed in Israel’s sustained campaign of air and artillery strikes on the crowded Palestinian enclave, sending black smoke billowing into the sky and razing entire city blocks.

The United Nations said 11 of its staff had been killed in Gaza since Saturday, while the International Red Cross and Red Crescent societies said it had lost five of its members.

In the occupied West Bank, at least four Palestinians were killed when armed Israeli settlers attacked a town south of Nablus, taking the death toll to 29, the Palestinian health ministry said.

Israel has massed forces, tanks and other heavy armour around Gaza in its retaliatory operation against what Netanyahu labelled “an attack whose savagery … we have not seen since the Holocaust”.

US President Joe Biden pledged to send more munitions and military hardware to its close ally Israel and expressed revulsion at the “sheer evil” of the slaughter of civilians in Hamas’s unprecedented assault.

Biden also made his first call for restraint over Israel’s response to the Hamas attacks, urging Israel to abide by the rules of war.

03:55

Soldiers find 'massacre' in Israeli village as air strikes continue to pummel Gaza

Soldiers find 'massacre' in Israeli village as air strikes continue to pummel Gaza

He said he had told Netanyahu it was “really important that Israel, with all the anger and frustration … they operate by the rules of war”.

The crisis, dubbed “Israel’s 9/11”, saw Netanyahu strike a political deal with Gantz and pledge to freeze for now his government’s judicial overhaul plan that has sparked unprecedented mass protests.

Opposition leader Yair Lapid has not joined the temporary alliance, although the joint statement said a seat would be “reserved” for him in the war cabinet.

Far-right National Security Minister Itamar Ben-Gvir wrote that he “welcomes the unity, now we must win”.

As the war raged on, fears mounted in Israel over the fate of at least 150 hostages – mostly Israelis but also including foreign and dual nationals – held in Gaza by Hamas.

The group has claimed that four captives died in Israeli strikes and threatened to kill other hostages if civilian targets are bombed without advance warning from Israel.

Hamas claimed Wednesday to have released an Israeli woman and her two children it said had been detained during fighting with Israeli forces, but Israeli television networks rejected the announcement.

Concern rose over the worsening humanitarian crisis in war-torn Gaza, where Israel had levelled over 1,000 buildings and imposed a total siege, cutting off water, food and energy supplies for 2.3 million people.

The enclave’s sole power plant shut down Wednesday after running out of fuel, Gaza’s electricity provider said.

More than 260,000 Gaza residents have been forced from their homes, a UN aid agency said, with secretary general of the world body, Antonio Guterres, voicing fears of a deterioration in an already dire humanitarian situation.

The European Union called for a “humanitarian corridor” to allow civilians to flee the enclave’s fifth war in 15 years.

Arab League foreign ministers meeting in Cairo called for aid to be allowed into Gaza “immediately”.

Israel appeared to be readying for a possible ground invasion of Gaza, but faces the threat of a multi-front war after also coming under rocket attack from militant groups in neighbouring Lebanon and Syria.

Israel again struck targets Wednesday in southern Lebanon, an area controlled by the Iran-backed Hezbollah.

On Wednesday evening, rocket sirens sounded across Israel’s north, and the army said there was a suspected aerial “infiltration” from Lebanon. It later backtracked, blaming an “error”.

Biden, who has diverted an aircraft carrier battle group to the eastern Mediterranean, has warned Israel’s enemies – state or group – not to get involved.

He urged Iran, which has long financially and militarily backed Hamas but insists it had no involvement in Saturday’s assault, to “be careful”.

A first US aircraft has delivered “advanced armaments” to southern Israel’s Nevatim Airbase, the Israeli army said.

Israel has been badly shaken by the deadliest attack since its creation in 1948 and the intelligence failure that allowed more than 1,500 militants to storm through the Gaza security barrier in their coordinated land, air and sea attack on the Jewish Sabbath.

Hamas gunmen swept into small towns and kibbutzim and indiscriminately killed residents who hid in their homes or died defending their communities.

Biden on Tuesday expressed his disgust at atrocities including murders of entire families, rapes of women and “stomach-turning reports of babies being killed”.

The US State Department said at least 22 US citizens had been killed, as Secretary of State Antony Blinken headed to Israel in a show of solidarity.

Israeli forces have retaken more than a dozen southern towns near Gaza after days of gruelling street battles that have left the bodies of at least 1,500 Hamas militants strewn in the streets.

Army spokesman Jonathan Conricus said they had discovered “a staggering 1,200 dead Israelis” – most of them civilians – as they went house to house.

The army later reported 169 fallen Israeli soldiers.

Troops have encountered and killed several holdout Hamas militants, said Israeli military spokesman Daniel Hagari, including 18 on Wednesday.

The Israeli army has called up 360,000 reservists for what Netanyahu has said will be a “long and difficult” war.

Israel’s intelligence minister Gila Gamliel said the war to “uproot” Hamas will deter militants from carrying out attacks across the world.

Heavy bombardment again rained down on Gaza, where the sky was blackened and Hamas said at least 30 people were killed in overnight strikes.

Rubble, burnt out cars and broken glass covered roads in Gaza City, where bombs struck the Hamas-linked Islamic University.

Also targeted were residential buildings, mosques, factories and shops, said Salama Marouf of the Gaza government’s media office.

Gaza resident Mazen Mohammad, 38, said his terrified family had spent the night huddled together as explosions shook the area, before emerging in the morning to assess the total devastation of their neighbourhood.

“We felt like we were in a ghost town, as if we were the only survivors,” Mohammad said.

Medical supplies, including oxygen, were running low at Gaza’s overwhelmed Al-Shifa hospital, said emergency room doctor Mohammed Ghonim.

Unrest has flared in the occupied West Bank, where protests have been held in solidarity with Gaza and 27 Palestinians have been killed in clashes since Saturday.

Israeli cities have been eerily quiet and tense, with some residents noting a growing sense of fear and distrust between Jews and members of the Arab-Israeli minority.

Frantic diplomacy has continued as international and regional powers sought to prevent a wider conflagration in the Middle East.

Additional reporting by Reuters and Associated Press