Government advice that Britons should avoid all but essential travel to Bangkok has been extended to the whole of Thailand because of "increasing tension" in the country.

The Foreign Office changed its travel advice relating to the Thai capital on Thursday because of fears over the safety of Britons, given the risk "that violence could break out without warning".

It followed a series of explosions near a massive encampment of anti-government protesters in Sala Daeng in Bangkok's business district which left dozens of people injured.

Thailand has seen growing tensions between red-shirted anti-government protesters and security forces, often ending in violent skirmishes.

At least 26 people have been killed and nearly 1,000 wounded in clashes and yesterday protesters forced Bangkok's elevated train system to close during rush hour.

The Foreign Office website said "substantial numbers of troops" were deployed in central Bangkok and there had been protests and violent incidents in other parts of Thailand including popular tourist destinations such as Pattaya, Chiang Mai, Chiang Rai and Ayuthaya in the past week.