Israel has bombed Gaza ahead of a potential ground assault against Hamas while US President Joe Biden condemned the Palestinian militant group's surprise attack as "sheer evil" and issued a warning seemingly aimed at its Iranian backers.
Israel's death toll reached 1200 with more than 2700 wounded, its military said, from Hamas gunmen's hours-long rampage after breaching the fence around Gaza on Saturday.
Retaliatory strikes on the blockaded enclave have killed 1055 people and wounded 5184, Palestinian officials say.
Israel has vowed swift punishment for the deadliest Palestinian militant attack in its history that left corpses strewn around a music festival and a kibbutz community.
On Saturday, Hamas gunmen from the Gaza Strip rampaged through parts of southern Israel, in the deadliest Palestinian militant attack in Israel's history.
Israel has vowed swift punishment for a militant attack that 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. "We started the offensive from the air, later on we will also come from the ground."
The Israeli military said its troops had killed at least 1000 Palestinian gunmen who infiltrated from Gaza.
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.
At the White House, Biden told reporters the United States had "enhanced our military force posture in the region to strengthen our deterrence," including by moving an aircraft carrier strike group and fighter aircraft.
"We stand ready to move in additional assets as needed," Biden said. "Let me say again to any country, any organisation, anyone thinking of taking advantage of the situation, I have one word: don’t," said Biden, in an apparent reference to Iran and its proxies in the region.
US officials say they do not have evidence Iran orchestrated the attacks, but point to Iran's long-term support for Hamas.
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 the Iron Dome aerial defence system. He called for Israel to follow the "law of war" in its response.
Biden also despatched his top diplomat Antony Blinken to Israel, who will depart for the region on Wednesday and meet with Israeli officials to deliver "a message of solidarity and support," State Department spokesperson Matthew Miller said.
Israeli Prime Minister Benjamin Netanyahu's right wing coalition and opposition leaders were close to forming an emergency unity government.
A meeting between Netanyahu and former Defence Minister Benny Gantz was scheduled for Tuesday but was delayed to Wednesday.
Countries including Fiji, South Korea, Denmark, the Czech Republic and Canada scrambled to evacuate citizens from Israel, many stranded after major airlines cancelled flights.
Palestinian media said Israeli airstrikes had hit homes in Gaza City, the southern city of Khan Younis and in the Bureij refugee camp in central Gaza. Residents on social media said many buildings had collapsed, sometimes trapping as many as 50 people.
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 dehumanisation 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 UN envoy Riyad Mansour wrote to the UN Security Council.
