Britain on Tuesday mobilised hundreds of soldiers to Cyprus to help its nationals evacuate following a significant escalation between Israel and Lebanon's Hezbollah, urging people to leave immediately.
As contingency plans are rolled out to support British nationals in Lebanon and the region, the Foreign, Commonwealth and Development Office (FCDO) said in a statement around 700 troops, backed by the border force, would move to Cyprus in the coming hours.
The air force also have aircraft and transport helicopters on standby to provide support if necessary, the FCDO added.
"Events in the past hours and days have demonstrated how volatile this situation is, which is why our message is clear, British nationals should leave now," said Defence Secretary John Healey.
Fierce fighting this week between Israel and the Iran-backed Lebanese Hezbollah has increased fears that nearly a year of conflict will explode and destabilise the Middle East, where a war is already raging in Gaza.
Israel has said it is shifting its focus from Gaza to the northern frontier, where Hezbollah has been firing rockets into Israel in support of Hamas, which like Hamas is also backed by Iran.
Israel's offensive since Monday morning has killed 569 people, including 50 children, and wounded 1,835 in Lebanon, Health Minister Firass Abiad told Al Jazeera TV.
Thousands of displaced people who fled from southern Lebanon were sheltering in schools and other buildings.