Britons should not travel to Syria unless it is absolutely necessary, the Government warned today.
The Foreign Office issued new advice for the Middle Eastern country after more than 170 protesters were killed in three weeks of unrest.
Foreign Office Minister Alistair Burt said today: "In light of the deteriorating security situation in Syria we have decided to change the overall level of our travel advice.
"We now advise against all but essential travel to Syria. This will take immediate effect.
"The safety of British nationals is always our primary concern.
"We recommend those in Syria exercise caution and maintain a high level of security awareness, particularly in public places and on the roads, and avoid large crowds and demonstrations."
International pressure is mounting on Syria's president, Bashar Assad, with key European governments and the United Nations denouncing a deadly crackdown that has failed to quell a popular uprising.
In the latest violence, security forces killed a student during a protest at Damascus University in the capital. There were conflicting reports about whether the student was shot or beaten to death.
Britain has joined the United States, France and Germany in demanding an immediate end to the bloodshed.
Protests erupted last month and have been growing steadily, with tens of thousands of people calling for sweeping reforms in one of the most authoritarian regimes in the Middle East. The Assad family has kept an iron grip on power for 40 years, in part by crushing dissent.
Foreign Secretary William Hague previously branded the violence "unacceptable", adding: "Political reform is the only legitimate response to demands from the Syrian people."