The British embassy in Libyan capital, Tripoli, has said it was aware of “a potential threat” against it.
It comes days after Britons were urged to leave the Libyan city of Benghazi because of a threat to Westerners.
The UK Foreign Office said: “We are aware of reports of a potential threat against the British embassy in Tripoli and we are liaising closely with the Libyan government.”
It already recommends against all but essential travel to Tripoli.
“There is no change to our travel advice,” the FCO said.
It gave no further details about the potential threat.
Four days ago Britons were urged to leave Benghazi immediately.
Germany and the Netherlands had also urged their citizens to leave Benghazi.
Speaking at the time about security problems, Libya’s deputy interior minister Abdullah Massoud said the situation did not warrant such a response.
The minister added he would be contacting the Foreign Office for further clarification and insisted such actions added to instability in the region.
The UK Foreign Office has been advising against travel to Benghazi and most parts of Libya since September.
Britain has not had a diplomatic presence in Benghazi – Libya’s second largest city – since an attack on the US consulate in Benghazi on 11 September when the US ambassador and three other Americans died.
Two weeks ago, in neighbouring Algeria, militants took over a gas plant, taking hundreds of people hostage and claiming they were acting in revenge for events in Mali.
It is thought 37 foreigners – including six UK nationals – died during the four-day siege, which ended after Algerian special forces stormed the compound.
The Foreign Office has also advised vigilance in Libya following French military intervention in Mali saying there was “a possibility of retaliatory attacks targeting Western interests in the region”.