The Foreign Office has advised against all travel to Bangkok as a crack-down on anti government protesters triggered more violence today.

The FCO had previously warned against all but essential travel to the city, but reviewed its advice amid escalating violence.

Although red-shirt demonstrators surrendered when soldiers attacked their camp, militant gangs set fire to key buildings in the city.

They set fire to the stock exchange, electricity headquarters, banks, government offices and Siam Theatre, a city institution.

The Thai Government extended a curfew until Sunday in Bangkok and in the 23 other provinces where a state of emergency is in place.

The FCO said: “British nationals already in Bangkok should stay indoors and monitor this travel advice and local media. British nationals elsewhere in Thailand should wherever possible take transport services which do not involve transiting Bangkok.”

It pointed out that Suvarnabhumi airport in Bangkok is operating as normal and travellers transiting Bangkok on their way to other destinations will be safe.

The FCO is also advising against all but essential travel to Chiang Mai.