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The UK is holding talks with the aviation industry to keep flights to Israel open as dozens of Britons attempt to return home.
It comes as other nations have sent in repatriation flights following the attack by Hamas on Israel at the weekend.
More than 900 people have been killed in Israel and around 700 in Gaza and the West Bank.
Israel has sealed the Gaza strip off from supplies of food, fuel, medicine and other staples, while launching retaliatory air strikes on the Hamas-ruled territory, which is home to 2.3 million people.
Britain's Foreign Secretary, James Cleverly, said a “significant number” of British-Israeli dual nationals have been caught up in the conflict.
He said the government is “standing ready” to support any British citizens who are concerned or whose loved ones have been “injured in any way”.
Mr Cleverly said ministers are “working with” the aviation industry to ensure commercial flights remain available to Britons looking to leave Israel.
However, on Tuesday those seeking to fly home were struggling to book flights.
Flights between Tel Aviv and the UK have either been cancelled, are fully booked or only have a few spare seats costing more than £1,200 each.
EasyJet usually serves Gatwick, Luton and Manchester Airports from the Israeli city but has paused operations on those routes.
Wizz Air, which normally connects Israel with Gatwick and Luton, has also suspended those flights.
Virgin Atlantic has cancelled one of its two daily return flights between Tel Aviv and Heathrow until at least Wednesday.
Its other daily return flights are still operating but there is no availability on its UK-bound services until next week.
British Airways is continuing to run flights between Tel Aviv and Heathrow, with adjusted departure times.
“We are closely monitoring the situation in Israel,” it said. “We’re keeping this situation under review.”
People wanting to book a seat on the next available flight are being charged £1,204 to travel on Wednesday, more than three times the price of a flight on the same route a week later, which is just £385.
Israeli flag carrier El Al has no availability on flights to the UK until next week.
As of Tuesday morning, about 47 per cent of flights were being cancelled to and from Tel Aviv's Ben Gurion Airport and 41 per cent were delayed, according to real-time flight tracker Flightradar24.com, which categorised the city as having the highest level of flight disruption in the world.
Etihad Airways has temporarily suspended operations until Wednesday. “The safety of passengers and employees is the highest priority for Etihad,” says a statement on the Abu Dhabi carrier's website.
“Etihad continues its policy of vigilance and continuing review, and is monitoring the situation closely through liaison with regulatory authorities and continuous intelligence reports. Any change to future operations will be communicated to affected guests immediately.”
Other global airlines pausing operations include Gulf Air, Swiss Air, United Airlines, Delta Air Lines, American Airlines and Cathay Pacific.
The UK Foreign Office has urged its citizens in Israel and Gaza to register their presence.
“If you are in Israel and the Occupied Palestinian Territories, you are advised to register your presence with the FCDO,” it said.
“The FCDO continues to advise against travel to parts of Israel and the Occupied Palestinian Territories, and to advise against all but essential travel to all other parts.”
On Tuesday, Cyprus’ Foreign Ministry announced it will act as a way station for foreign nationals fleeing Israel.
A crisis management team composed of its foreign affairs, defence, interior and justice ministers decided to activate a plan to help evacuees from Israel reach their home countries through Cyprus, it said in a statement.
The move will see Cyprus provide accommodation and other facilities to foreign nationals to help in their repatriation.
Eighty five citizens of Portugal and Spain arrived in Cyprus from Israel on the first evacuation flight early Tuesday on a Portuguese air force plane, a foreign ministry spokesperson said. A second flight was planned for later in the day.
Cyprus’ proximity to the Middle East and Africa has in the past made it a ready transfer point for evacuees from war-torn countries.
In April, it received hundreds of United Kingdom citizens evacuated from war-battered Sudan before they returned to Britain. In 2006, Cyprus hosted tens of thousands of foreign nationals fleeing war in Lebanon following Israel’s attack on Hezbollah.
Other nations have already begun evacuating citizens.
Italy evacuated 200 citizens on two military flights on Tuesday morning and another 180 people were expected to arrive in Verona on a private flight later.
Austrian Chancellor Karl Nehammer said an air force transport plane would be sent to Cyprus on Wednesday to pick up Austrians who want to leave Israel.
Once they have arrived in Cyprus, they can continue their journey on scheduled flights. The Foreign Ministry called on Austrians wanting to take evacuation flights to register with the embassy in Tel Aviv.
Poland, Hungary and Romania already have flown citizens out of Israel.
Romania’s Ministry of Foreign Affairs said 596 citizens were repatriated from Israel on four flights on Monday night. Around 600 people had been flown back to Romania over the weekend.
