Flights have been organised to get British nationals out of Israel, the Foreign Office has said, with the first plane set to leave Tel Aviv on Thursday.
A rapid deployment team is also on its way to assist British citizens on the ground.
Vulnerable people are prioritised, according to the Foreign Office, and commercial flights will be helped to the UK to bring back British nationals trying to leave the country.
Those eligible for the flights will be contacted directly and British nationals should not make their way to the airport unless they are called, the government added.
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At least 2,400 lives have been claimed in the war, which was ignited by a bloody and wide-ranging Hamas attack on Israel at the weekend, and concerns remain for Brits still there.
Jake Marlowe, 26, became the fourth Briton to be confirmed killed on Wednesday, with at least 17 UK nationals in total reported either dead or missing.
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The Foreign Office, which has said family members of its diplomats are leaving Israel as a “precautionary measure”, has advised against all but essential travel to the country.
At least 100 people are believed to have travelled from the UK to Israel to serve in the military there according to the Israeli Embassy in the UK.
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British families of Israeli hostages, meanwhile, said the Hamas invasion of Israel amounts to a “second Holocaust”.
The mother of Noam Sagi, 53, and the parents of Sharon Lifschitz, 52, were taken hostage after Hamas fighters entered Kibbutz Nir Oz near the border with Gaza on Saturday.
Mr Sagi told reporters he should be celebrating his mother Ada’s 75th birthday and said the situation has created “the biggest hostage crisis the world has faced in decades”.
Ms Lifschitz described how her parents, whom she is not naming out of fear for their safety, have fought for peace in the region all their lives.
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It comes as Israel continues to bombard Gaza, where Israeli citizens are held hostage and the UN reports 340,000 people have been left displaced.
Rescue workers warn the situation is made more dire as Israel continues to block goods from entering the Gaza Strip, where 2.3 million people live.
The Red Cross has pleaded for fuel to be allowed in to prevent hospitals from “turning into morgues”, but Israel says it will not break its siege until all captives taken by Hamas are freed.
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Meanwhile, Israeli Prime Minister Benjamin Netanyahu described Hamas is the “enemy of civilisation” and vowed the group will be “crushed”.
Speaking alongside US Secretary of State Antony Blinken in Israel on Thursday, Mr Netanyahu said the militant group should be treated “exactly as ISIS was treated”.
He said “no country should harbour” Hamas militants – and those that do should be sanctioned – as he condemned the “murder of children in front of their parents”, the “burning of people alive” and “beheadings”.
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