The Foreign Office has extended its travel warning to all parts of Thailand due to the “increasingly volatile” political crisis.
The FCO last week advised UK travellers against all but essential travel to Bangkok, and has now extended this to all parts of the country.
The advice reassured travellers that Bangkok airport is safe and that the violence is not directed at foreigners.
According to the latest reports, Thai security forces and Red Shirt protesters have opened fire on each other. A conflict occurred on the outskirts of the city centre when the authorities tried to stop the protesters widening their demonstrations.
Hundreds of Red Shirts had formed a convoy to leave their camp in central Bangkok to stage a rally at the Talad Thai market, 30 miles away. It is not yet known whether anyone was injured.
The clash is the latest development in six weeks of demonstrations by anti-government protesters, who want prime minister Abhisit Vejjajiva to step down.
The stand-off has prompted many luxury hotels in central Bangkok to close, including the Four Seasons and Intercontinental.