The blasts were caused by grenades, but it was not clear who fired them, according to reports.
Thai Prime Minister Abhisit Vejjajiva has called an emergency meeting with security chiefs.
Many British holidaymakers are in the city including a group of Princess Cruises passengers who are due to be flown home tomorrow.
The Foreign and Commonwelath Office amended its travel advice, saying: "We advise against all but essential travel to the city of Bangkok in the light of ongoing political demonstrations.
"The advice reflects our concern for the safety of British nationals planning to travel to Bangkok, given the risk that violence could break out without warning during the increasingly volatile political crisis.
"The situation is changing on a daily basis, and we recommend that british nationals living in Thailand or travelling to the country check our travel advice regularly for details of further developments.
"The advice does not apply to passengers tranisting Bangkok airport on their way to other destinations in Thailand or internationally."
The FCO added that the Bangkok’s Suvamabhumi airport is operating as normal and the route from the city remains open.
*See linked story.
by Phil Davies
