British residents still in Syria have been warned to leave as soon as possible by the Foreign & Commonwealth Office.
The warning comes as violent disturbances in urban centres across the country, including the capital Damascus, continue.
Military operations and clashes between protestors and security forces have resulted in a significant number of deaths, the FCO said.
“Those who choose to remain in Syria, or to visit against our advice should be aware that it is highly unlikely that the British Embassy would be able to provide a normal consular service in the event of a further breakdown in law and order and increased violent civil disorder.
“Evacuation options would be limited because of likely communication and travel restrictions,” added an FCO statement.
It is likely road networks may be blocked during disturbances or demonstrations.
Several major highways including Tartous-Latakia, Tartous-Homs, Latakia-Aleppo, Homs-Hama, Homs-Damascus and Damascus-Jordan have been temporarily closed because of demonstrations or disturbances.
There has also been an increase in the number of security force checkpoints on major road routes.
There is an increased likelihood of large gatherings on public holidays and at weekends, particularly in the hours following Friday prayers.