The UK Foreign Office has advised people to avoid non-essential travel to a region of Syria hit by riots which have left 25 people dead.
A spokeswoman said the advice was not related to terrorism although a general warning over the danger of terrorist activity in Syria is already in place.
The new advice relates to the north-east province and the town of Qameshli.
The unrest began with brawling before a football match between teams supported by Arabs and Kurds on 12 March.
Wave of protests
The clashes, in which more than 100 people have also been injured, have triggered a wave of protests among Syrian Kurds living in exile.
They claim the authorities have encouraged violence against the Kurdish minority in the disturbances.
The Foreign Office said only about 800 Britons were understood to be resident in Syria and a couple of hundred holidaying there.
Only a handful of oil workers were thought to be in the area affected by the new advice.
The existing Foreign Office travel advice for Syria says there is a high threat to Western interests from terrorism, as in other places in the Middle East, and urges vigilance in public places.