Foreign Office advises people to take next available flight as it tries to secure seats amid escalating violence

A Unicef representative said essential services of water and healthcare in Beirut were being rapidly depleted. Photograph: Hussein Malla/AP

British nationals in Lebanon have been urged to leave the country immediately as the violence escalates between Israel and Hezbollah.

The Foreign, Commonwealth and Development Office (FCDO) said on Friday night that British nationals in Lebanon should leave on the next available flight.

It added: “We are working to increase capacity and secure seats for British nationals to leave.”

British nationals in Lebanon should register their presence on the FCDO’s website to stay up to date with the latest information, it said in a statement.

On Saturday, the Israeli government said it had killed Hassan Nasrallah, the leader of Lebanese militant group Hezbollah, with the Israeli Defence Forces posting on X that he would “no longer be able to terrorise the world”.

It comes after a series of massive explosions levelled multiple apartment buildings in Beirut on Friday night.

There are an estimated 5,000 British nationals and immediate family members in Lebanon. Of those, several hundred are believed to be UK single nationals.

Ettie Higgins, Unicef’s deputy representative in Lebanon, said “thousands and thousands” of people had fled southern Beirut, while hospitals were “overwhelmed” and water pumping stations had been destroyed.

“Even the most basic essential services of healthcare and water are now being rapidly, rapidly depleted,” she told BBC Radio 4’s Today programme on Saturday.

“There was already a humanitarian crisis in Lebanon given that it’s been hosting over 1 million refugees from Syria for over a decade, so it’s rapidly escalating into a catastrophe.”

She added that 50 children had been killed, and that she expected the figure to rise as the airstrikes continued. Israel has insisted the strikes have targeted Hezbollah military installations or senior figures.

The UK defence secretary, John Healey, said that the fighting presented a “risk that this escalates into something that is much wider and much more serious”.

The Israeli army chief, Lt Gen Herzi Halevi, told troops on Wednesday that ongoing airstrikes were “to prepare the ground for your possible entry and to continue degrading Hezbollah”.

Asked about the potential ground invasion on Friday, Healey replied: “We’re watching this really carefully. That will be a matter for the Israelis. At the moment, it’s airstrikes. At the moment, there are missiles from the Lebanese Hezbollah directed at Israel. This conflict serves no one.”

Healey said his first concern was the safety of British nationals in Lebanon. “The travel advice remains the same – don’t go to Lebanon. If you are in Lebanon, then get out, and there are still commercial flights leaving so people can do that.

“But I left Labour conference earlier this week to chair a Cobra committee in government because we are making the preparations you’d expect of government ahead of any potential developments in the future.”

According to the PA Media news agency, the government has successfully asked airlines to increase capacity on routes out of Lebanon, with FCDO teams in Beirut ordered to support the British consulate.

It is thought they are ready to facilitate evacuations by sea or air, which could be triggered if the security environment degrades further and British nationals are no longer able to leave via other routes.