Israel said it is conducting a "large-scale strike" on Hamas targets in Gaza as Prime Minister Benjamin Netanyahu formed an emergency unity government with former defence minister Benny Gantz.

While the country is "preparing for the next stages of war", the IDF's (Israeli Defence Forces) international spokesperson Lt Col Richard Hecht said no decision has been made on a ground operation yet.

"Anyone who will come near the fence will be shot - anyone," he said, adding Hamas is still trying to come into Israel through the sea. "No one's coming in, no one's coming out."

Hamas media claims 15 Palestinians were killed in a round of air strikes on Thursday, which they said was the third on residential buildings in the past few hours and came without warning.

Israel's president, Isaac Herzog, meanwhile told reporters the bodies of civilians killed by Hamas militants have shown signs of torture "unlike anything they'd ever seen".

Israel ready for two front war - follow live conflict updates

As threats escalate, Israeli flag carrier El Al said it would operate 12 extra flights on Wednesday and Thursday to and from Athens, Rome, Madrid, Bucharest, New York, Paris, Larnaca and Istanbul.

El Al had already announced an additional flight from New York and six flights to and from Larnaca, while its low-cost unit Sun Dor also plans flights from Istanbul.

Most foreign airlines have suspended or curtailed services, leaving passengers uncertain how to leave or reach the country and consular services struggling to keep up with demand for assistance, with priority given to those with missing relatives.

Air France and Lufthansa are pressing ahead with flights on Thursday, but Norwegian Air cancelled an evacuation flight from Tel Aviv due to a lack of insurance cover and Dutch airline KLM pulled out over safety concerns.

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Israel's parliamentary finance committee has said it would debate authorising state guarantees for providing war risk insurance for Israeli airlines.

The panel said insurance companies had indicated they were entitled to cancel cover with seven days' notice. Airline executives said some cover was still available.

A senior official at insurance industry body Lloyd's Market Association said Israel is not on a commonly used list of high-risk areas for aviation, but it made sense for underwriters to seek to control their exposure, given the escalating violence.

British Airways said it would suspend flights to Tel Aviv after diverting a flight from London back to Britain shortly before it was due to reach Israel, citing security concerns.

The UK government has also ordered the families of its diplomats in Israel to leave.

'Where shall I go?'

Evacuation efforts come as the combined death toll reported by both sides reached more than 2,000 people, following the weekend attacks by a militant faction of Palestinian political group Hamas and retaliatory strikes by Israeli forces.

It's also left about 340,000 people displaced, according to the UN, with a mother in Gaza who sought sanctuary at her daughter's house during an Israeli strike left in tears as she returned home to find it "bombed entirely".

"There's nothing left," she told a Sky News team in Gaza.

"There's nothing visible in the house. It's been bombed entirely... where shall I go?"

Meanwhile, there are calls for a humanitarian corridor out of Gaza as the bombardment of the Hamas-controlled Gaza Strip continues.

The UN Middle East envoy is currently in Cairo working with other key regional and international partners and the Egyptian government on ending the Israel-Hamas conflict, preventing its expansion, and opening a humanitarian corridor to deliver fuel, food and water to Gaza.

Israel cut off the supply of water and electricity to Gaza earlier in the week and said on Thursday it won't life the total block until all hostages Hamas captured in its weekend attack are freed.

The Red Cross has pleaded for fuel to be allowed in to prevent overwhelmed hospitals from "turning into morgues", and believes supplies could run out in hours.

Tor Wennesland, the UN's special coordinator for the Middle East peace process, is following up on Egypt's offer to facilitate humanitarian access through the Rafah crossing and to make the El Arish airport available for critical assistance, a UN spokesman said.

More than 1,000 housing units in Gaza have been destroyed and about 560 severely damaged and rendered uninhabitable in the past day, the UN said.

The US is also in active conversations to achieve safe passage out of Gaza for civilians, White House National Security spokesman John Kirby said Wednesday.

Mr Kirby noted Israel and Egypt are the two most significant players in the efforts.

"We are having active conversations about trying to allow for that safe passage," he said. "It's the civilians who did nothing wrong so we want to make sure they have a way out."