Britain warned its nationals Thursday against all but essential travel to the Thai capital Bangkok due to the "increasingly volatile" situation on the streets.

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," it said.

"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."

A series of suspected grenade attacks rocked Bangkok's business district on Thursday, leaving at least 45 people injured including foreigners, amid a stand-off between groups of rival protesters.

Around 812,000 British nationals visited Thailand in 2008, the Foreign Office said, citing Tourism Authority of Thailand figures.