The Bahrain government has imposed a three month state of emergency on the Gulf kingdom, following a crackdown on anti-government protesters.
The British Foreign and Commonwealth Office (FCO) has heightened its travel advice and is now warning against all travel to Bahrain until further notice.
Media reports say there have been a number of deaths in the capital Manama, after soldiers and riot police cleared protesters from Pearl Square.
British nationals without a pressing need to stay are being told by the FCO that they should be ready to leave “at short notice”, on commercial flights.
There have been rumours of possible evacuation plans if the situation deteriorates further.
Bahrain's flag carrier Gulf Air is continuing to operate nearly all its flights, except services to and from Iran and Iraq, but is advising passengers to allow extra time when travelling to Bahrain International airport.
Its downtown sales office in Manama and Seef Mall are currently closed, but the airport ticket office is open 24 hours.
British Airways is also continuing its daily flights to Bahrain, but is monitoring the situation closely and is is advising passengers to check with the FCO, a BA spokesman told ABTN.
“We are offering a daily service still, and we’re offering customers the opportunity of rebooking to alternative destinations or flying at another time,” he said.
“We’re keeping a very close eye on what is happening there and there may be further changes in the next day or so, dependent upon what happens in the principality.”