He said the situation on the ground is "fast-moving" and ministers can't guarantee help "if things escalate in a major way over the coming hours and days".

Follow live: Heavy fire in Lebanon towns near Israeli border - reports

There are concerns about rising violence in the Middle East after Hezbollah leader Hassan Nasrallah was killed in Israeli airstrikes in Beirut at the weekend.

The Iran-backed militant group responded by saying it is ready to fight should Israel launch a ground offensive, with fears mounting that the escalating hostilities could result in a full-scale regional war.

Mr Lammy said the government had set up a rapid response unit to help the estimated 5,000 British citizens in Lebanon, with 700 troops stationed in Cyprus and seats booked on commercial flights to bring them home.

He told reporters on Monday night: "I have been urging since coming to office in July for British nationals to leave Lebanon. And indeed the previous government from October 2023 was urging UK nationals not to travel to Lebanon.

"Notwithstanding that we sent a rapid response team. 700 troops are in Cyprus. We will do all we can to assist people to get out. We have secured places on commercial flights that are flying tomorrow so that UK nationals can get out."

Mr Lammy urged British citizens in Lebanon to make use of this help immediately, saying the government might not be able to protect them if the conflict escalates.

Asked what he would say to British nationals who have not yet taken his advice, he said: "I urge them to leave because the situation on the ground is fast-moving."

He added: "While we will do everything we can to protect British nationals and those plans are in place to do so, we cannot anticipate the circumstances of the speed with which we could do that if things escalate in a major way over the coming hours and days."

It emerged today that Israeli special forces are conducting probing operations inside Lebanon, ahead of a potential ground assault.

Earlier on Monday, Israel's defence minister Yoav Gallant warned "the next stage in the war against Hezbollah will begin soon".

Mr Lammy said he spoke to US Secretary of State Antony Blinken on Monday evening and they are both "concerned" about the comments and are urging de-escalation.

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Asked if military aid could be sent to Israel if it is attacked by Iran, which backs Hezbollah, the cabinet minister said he met with the Iranian foreign minister last week "and we had a detailed discussion and of course, I was urging Iran to show restraint".

"As you would expect over the coming hours, we will continue to be in touch with Iran," he added.

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On whether he agrees with US President Joe Biden that the killing of Hassan Nasrallah was a "measure of justice", he said: "I don't mourn the death of the head of a proscribed terrorist organisation, but I do mourn the civilians who have lost their lives in the bloodshed over the last few days."