The Foreign Office on Thursday urged Britons in the eastern Libyan city of Benghazi to leave, citing a "specific and imminent threat" to Westerners.
Britain has warned its citizens against travelling to most parts of Libya since September, after an attack on the US consulate in Benghazi killed ambassador Christopher Stevens and three embassy staff.
"We are aware of a specific, imminent threat to Westerners in Benghazi," the Foreign Office said. It said that France's military intervention against Islamist rebels in Mali had heightened the possibility of attacks against Westerners in North Africa.
Thirty-seven foreign workers from eight countries were killed last week in an attack on an Algerian gas facility by Islamist militants opposed to France's operations in Mali.