The prime minister has told British nationals in Lebanon “now is the time to leave”.

Sir Keir Starmer said “we are ramping up the contingency plans, I think you’d expect that in light of the escalation”, and added that UK citizens should “leave immediately”.

The Ministry of Defence (MoD) is sending 700 troops to nearby Cyprus to prepare for the possible evacuation of British nationals from Lebanon and the government “continues to advise against all travel to Lebanon”.

The situation in the country is described as deteriorating “rapidly, with devastating consequences”.

Asked by reporters how the prime minister will ensure the situation isn’t a repeat of the chaos in the Afghan capital Kabul when the Taliban seized control in August 2021, Sir Keir said: “The most important message from me to British nationals in Lebanon is to leave immediately.

“It is important that we’ve been really, really clear: now is the time to leave.”

A senior government source added that the difference, for now at least, is there are commercial flights leaving Lebanon.

Ministers have repeated their call for an immediate ceasefire.

They say more than 500 people have been killed in Lebanon in the past 24 hours.

The Defence Secretary John Healey said: “We continue to urge all sides to step back from conflict to prevent further tragic loss of life.

“Our government is ensuring all preparations are in place to support British nationals should the situation deteriorate.

“I want to thank the British personnel who are deploying in the region for their commitment and professionalism.”

Healey held a meeting with fellow ministers, intelligence chiefs and diplomats on Tuesday afternoon to work through the government’s plans.

Officials say the UK already has a significant diplomatic and military presence close to Lebanon, including RAF Akrotiri in Cyprus and two Royal Navy ships – RFA Mounts Bay and HMS Duncan – which have been in the eastern Mediterranean over the summer.

The Royal Air Force also has planes and helicopters on standby.

The escalating conflict in the Middle East is likely to be a significant topic of discussion for the prime minister and other world leaders at the UN General Assembly.

Sir Keir arrives in New York on Wednesday morning.

Tensions have been growing across the Middle East since Hamas gunmen attacked Israel on 7 October last year, killing about 1,200 people and taking 251 others as hostages.

Previously sporadic fighting between Israel and Hezbollah escalated on 8 October – the day after Hamas’s unprecedented attack. Hezbollah fired at Israeli positions, in solidarity with Hamas.

Hezbollah has launched more than 8,000 rockets at northern Israel and the Israeli-occupied Golan Heights. It has also fired anti-tank missiles at armoured vehicles and attacked military targets with explosive drones.

Last week Hezbollah’s communication devices started exploding all across Lebanon.

Israel then launched a massive series of air strikes on Monday that have so far killed 560 people according to the Lebanese government.

Last year, the British government helped co-ordinate the evacuation of British nationals from Gaza, with some 200 UK citizens thought to be living in the territory before the war broke out.

Israel’s military campaign in Gaza has killed more than 41,000 people since 7 October, according to the Hamas-run health ministry.