Man in yellow shirt is Bangkok bomber: Police

Workers clean a statue of Hindu god Brahma at the Erawan shrine, the site of a deadly blast in central Bangkok, Thailand, August 18, 2015. [Photo/Agencies]

It detonated at the Erawan Shrine, which is dedicated to the Hindu god Brahma, but is extremely popular among Thailand's Buddhists as well as Chinese tourists. Although Thailand is predominantly Buddhist, it has enormous Hindu influence on its religious practices and language.

Bangkok has been relatively peaceful since a military coup ousted a civilian government in May last year after several months of sometimes violent political protests against the previous government.

At the same time, the military government has tightly controlled dissent, arresting hundreds of its opponents and banning protests. Tensions have risen in recent months, with the junta making clear that it may not hold elections until 2017 and wants a constitution that will allow some type of emergency rule to take the place of an elected government.

Stirring the pot has been exiled former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 coup. It was his sister Yingluck Shinawatra who was ousted as prime minister last year.

Last week, Thaksin posted a message on YouTube urging his followers to reject the draft constitution because he said it was undemocratic. The draft charter is supposed to be voted on next month by a special National Reform Council. If it passes, it is supposed to go to a public referendum around January.

The US Embassy in Bangkok issued an emergency message for US citizens, advising them to avoid the shrine's area. In Washington, State Department spokesman John Kirby expressed deep sympathy to those affected by the Bangkok explosion. He said authorities were still determining whether any Americans were among the victims.

Tourists reacted with concern.

"We didn't think anything like this could happen in Bangkok," said Holger Siegle, a German who said he and his newlywed wife had chosen Thailand because it seemed safe. "Our honeymoon and our vacation will go on, but with a very unsafe feeling."