Britain warned its citizens Friday against all but essential travel to Lebanon due to a "heightened risk of anti-Western sentiment" linked to the possibility of military action against Syria.
The Foreign Office changed its travel advice following last week's attacks in the northern port city of Tripoli.
Last Friday, bombings outside two Sunni mosques in Tripoli killed more than 40 people -- the deadliest attack in Lebanon since its 1975-1990 civil war.
"We have today changed our travel advice to Lebanon to advise against all but essential travel. This is based on the recent upsurge in violence in Lebanon and regional tensions," a Foreign Office spokesman said.
"There may be a heightened risk of anti-Western sentiment in certain countries linked to the possibility of military action in Syria.
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"We advise UK nationals to be vigilant, to avoid any protests or demonstrations and to keep up to date with developments."
He urged British nationals to consider leaving "if their presence in Lebanon is not essential".
"We continue to advise against all travel to the Lebanese city of Tripoli, Palestinian refugee camps, the eastern Bekaa valley and southern suburbs of Beirut."
Britons are advised against all travel within five kilometres (three miles) of the Syrian border.
Coming a week after a deadly blast that hit the Beirut bastion of Shiite movement Hezbollah, the Tripoli bombings risk further stoking tensions between supporters and foes of the Syrian government.
"There is a high threat from terrorism. Attacks could be indiscriminate, including in places frequented by foreigners like hotels and restaurants," the Foreign Office said.
The change of travel advice came after British lawmakers voted Thursday against military action in Syria in a stunning defeat for Prime Minister David Cameron.