While U.S. President Joe Biden branded the Palestinian militant group’s surprise attack as “sheer evil” and offered a warning that appeared to be directed at its Iranian sponsors, Israel bombed Gaza overnight in preparation for a potential ground offensive against Hamas.

After breaking through the border barrier separating Israel and Gaza on Saturday, Hamas militants went on an hours-long rampage that left more than 2,700 people injured, according to Israel’s military.

The group’s armed wing, the Al Qassam Brigades, said it was still fighting inside Israel on Wednesday, as Israeli tanks and armoured vehicles assembled in large numbers just north of Gaza. and Hamas’ armed wing.

Retaliatory strikes on the blockaded enclave have killed 1,055 people and wounded 5,184, Palestinian officials say.

Israel has vowed swift punishment for the deadliest Palestinian militant attack in its history, which left corpses strewn around a music festival and a kibbutz community.

The military said dozens of its fighter jets struck more than 200 targets in a neighbourhood of Gaza City overnight that it said had been used by Hamas to launch its attacks.

“Hamas wanted a change and it will get one. What was in Gaza will no longer be,” Defence Minister Yoav Gallant told soldiers near the fence on Tuesday. “We started the offensive from the air, later on we will also come from the ground.”

Israel has put Gaza under “total siege” to stop food and fuel reaching the enclave of 2.3 million people, many poor and dependent on aid. Hamas media said on Wednesday electricity went out after the only power station stopped working.

With Palestinian rescue workers overwhelmed, others in the crowded coastal strip joined the search for bodies in rubble.

“I was sleeping here when the house collapsed on top of me,” one man cried as he and others used flashlights on the stairs of a building hit by missiles to find anyone trapped.

The Israeli military said its troops had killed at least 1,000 Palestinian gunmen who infiltrated from Gaza.

Scores of Israelis and others from abroad were taken to Gaza as hostages, some of whom were paraded through streets. Both sides have said many women and children were among the dead and wounded, and distraught relatives have held multiple funerals.

Israel said it was shifting all schools to remote learning from Sunday and stepping up issuing firearms to licensed citizens, predicting possible friction between its majority Jews and Arab minority amid calls for more protests in support of Gaza’s Palestinians.

In another sign of the crisis widening, Israeli shelling hit southern Lebanese towns after a rocket attack by the powerful armed group Hezbollah, which is backed by Iran. It was the fourth consecutive day of violence there and followed shelling from Syria on Tuesday that Israel said it was investigating.

RISKS AHEAD

A ground offensive carries risks for Israel, notably to the hostages held in the narrow, densely populated Gaza Strip that is tightly controlled by Hamas. It has threatened to execute a captive for each home hit without warning.

Palestinian sources said one of the homes Israeli air strikes hit in Gaza overnight killed three relatives of Hamas military wing chief Mohammed Deif, the secretive mastermind of the assault, planned for two years.

Israel withdrew from Gaza in 2005 after 38 years of occupation. Since Hamas seized power there in 2007, Israel has kept it under blockade, creating conditions among its inhabitants which Palestinians say are intolerable.

Washington said it was talking with Israel and Egypt about the idea of safe passage for civilians from Gaza, with food in short supply.

Hussein Al-Sheikh, an official in the West Bank-based Palestinian Authority, called on the international community to intervene urgently, saying Gaza faced “a major humanitarian catastrophe”.

INTERNATIONAL REACTION

At the White House, Biden called the Hamas attacks “an act of sheer evil” and said Washington was rushing additional military assistance to Israel, including ammunition and interceptors to replenish its Iron Dome aerial defence system.

He urged Israel to avoid causing civilian casualties and said the U.S. had strengthened its presence in the region by moving an aircraft carrier strike group and fighter aircraft.

“Let me say again to any country, any organization, anyone thinking of taking advantage of the situation, I have one word: don’t,” said Biden, in an assumed reference to Iran and its proxies.

U.S. officials say they do not have evidence Iran orchestrated the attacks, but point to the Islamic Republic’s long-term support for Hamas.

With Israel on a war footing, Prime Minister Benjamin Netanyahu’s right-wing coalition and opposition leaders were close to forming an emergency unity government.

Countries including Fiji, South Korea, Denmark, the Czech Republic and Canada scrambled to evacuate citizens from Israel, many stranded after major airlines cancelled flights.

‘WE HAVE DONE NOTHING’

Palestinian media said Israeli air strikes had hit homes in Gaza City, the southern city of Khan Younis and the Bureij refugee camp in central Gaza. Residents on social media said many buildings had collapsed, sometimes trapping as many as 50 people. Gaza’s hospitals were filled with casualties.

Wounded Palestinian Ala al-Kafarneh said he had lost eight family members when they were caught by an Israeli attack after fleeing two others. “A strike hit us and we don’t know why, we have done nothing,” he said.

The United Nations said more than 180,000 Gazans had been made homeless, many huddling on streets or in schools.

The Palestinian Foreign Ministry said Israeli strikes had since Saturday destroyed more than 22,600 residential units and 10 health facilities and damaged 48 schools.

“Such blatant dehumanization and attempts to bomb a people into submission, to use starvation as a method of warfare, and to eradicate their national existence are nothing less than genocidal,” Palestinian U.N. envoy Riyad Mansour wrote to the U.N. Security Council.

Violence also flared in Arab East Jerusalem and the Israeli-occupied West Bank, where officials say 21 Palestinians have been killed and 130 injured in clashes with Israeli forces since Saturday.