Western nations, including the United Kingdom, France, and Italy, have urged their citizens in Lebanon to leave without delay amid escalating tensions in the Middle East following the killing of Hamas and Hezbollah leaders last week, which Iran has blamed on Israel.

The assassination of Hamas political chief Ismail Haniyeh in Teheran on Wednesday, following shortly after Israel's killing of Hezbollah's military leader Fuad Shukr in Beirut, has prompted vows of retribution from Iran and its allied groups.

Iran has promised a "severe" response against Israel, which it holds responsible for Haniyeh's death. Israel has openly acknowledged killing Fuad Shukr, but has refrained from making any statement regarding the death of the Hamas leader Haniyeh.

Western officials are concerned that Hezbollah, an Iran-supported Lebanese organization, might be central to Iran's retaliation plans, potentially provoking a significant Israeli counteraction, reported the BBC.

UK Foreign Secretary David Lammy told British nationals in Lebanon. "Tensions are high, and the situation could deteriorate rapidly. While we are working round the clock to strengthen our consular presence in Lebanon, my message to British nationals there is clear — leave now."

France advised its citizens to exit Lebanon promptly, citing the "very volatile security context".

Italy's Foreign Minister Antonio Tajani urged Italians in Lebanon to return to Italy as soon as possible by commercial flights, "given the deteriorating situation".

Sweden's Foreign Minister Tobias Billstrom closed the nation's embassy in Beirut and urged Swedes to leave Lebanon immediately, stating: "The foreign ministry has instructed its staff to leave Beirut and travel to Cyprus, and the foreign ministry is planning a temporary relocation of its embassy."

The US embassy in Lebanon advised citizens to promptly book their departures.

"We encourage those wishing to leave Lebanon to book any available ticket, even if that flight does not depart immediately or does not follow the itinerary of their choice," it said via an email to citizens, cited by the Financial Times newspaper.

Lebanon's capital, Beirut, has seen a surge in departures from the country's only commercial airport, with long lines of travelers seeking to leave following the official advisories, said the FT.

Numerous airlines have altered operations to and from Beirut, with some suspending, rescheduling, or canceling flights. Among these are Air France-KLM Group, Kuwait Airlines, Lufthansa Group, Aegean, Emirates, and Qatar Airways. Additionally, certain airlines have suspended services to Israel.

Following the Hamas Oct 7 attacks, which killed more than 1,190 people in Israel and led to about 250 hostages being taken, Israel responded by launching a large-scale offensive against Hamas in Gaza.

Since then, the Hamas-run health ministry reports at least 39,583 Palestinians have been killed, and 91,398 injured. Of the original hostages, around 120 are thought to remain in Gaza, with the Israeli authorities having declared some dead.