The Foreign Office has advised Britons against all travel to Bahrain after confrontations between anti-government protesters and police intensified over the weekend.
Officials warned that all UK nationals should remain at home until further notice, amid reports that Saudi National Guard soldiers are about to enter the Gulf state.
The FCO said in a statement: "Following an increase in protests over recent days, confrontations between protesters and police, reports of protesters establishing roadblocks, and reports that the Saudi National Guard will enter Bahrain, we advise British nationals currently in Bahrain to remain at home until further notice.
"The risk of further outbreaks of violence has increased. If British nationals do travel within Bahrain they should maintain a high level of security awareness, particularly in public places and on major highways, and avoid large crowds and demonstrations."
Government officials had previously advised against all but essential travel, but amended their advice following clashes in the capital, Manama, on Sunday.
The island country has seen a month of unrest with anti-government demonstrators demanding the reform of the monarchy.
The Foreign Office has revoked a series of defence equipment export licences for Libya and Bahrain in the wake of the government crackdowns on protesters there.