Britons should avoid all but "essential" travel to Bangkok, the Government warned.
The Foreign Office has changed its travel advice relating to the Thai capital because of fears over the safety of British nationals, given the risk "that violence could break out without warning".
It follows a series of explosions near a massive encampment of anti-government protesters in Sala Daeng in Bangkok's business district. The blasts left dozens of people injured.
In a statement, the Foreign Office said: "At 15.45 today, the Foreign Office amended its travel advice to advise against all but essential travel to Bangkok.
"This 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 the travel advice on the Foreign Office website regularly for details of further developments."