Thai authorities said on Tuesday they were looking for a suspect seen on closed-circuit television (CCTV) footage near a renowned shrine where a bomb blast killed 22 people, including nine foreigners from several Asian countries.
The government said the attack during the Monday evening rush hour, in the capital's bustling commercial hub, was aimed at destroying the economy. No one has claimed responsibility.
National police chief Somyot Pumpanmuang said the suspect was wearing a yellow shirt and could be Thai or a foreigner.
"That man was carrying a backpack and walked past the scene at the time of the incident. But we need to look at the before and after CCTV footage to see if there is a link," Somyot told a news conference.
Police earlier said they had not ruled out any group, including elements opposed to the military government, for the bombing at the Erawan shrine on Monday evening, although officials said the attack did not match the tactics of Muslim insurgents in the south.
Prime Minister Prayuth Chan-ocha also referred to the man as a suspect without giving details. He said there were "still anti-government groups out there", although he did not elaborate.
Police were deployed to the blood-splattered site on Tuesday, some wearing white gloves and carrying plastic bags, searching for clues to an attack that could dent tourism and investor confidence.
The Thai baht fell 0.57 percent to 35.57 baht, its weakest in more than six years, on concern the bombing may scare off visitors. Thai stocks fell as much as 3 percent.
Police said the death toll was 22, with 123 people wounded. They said the blast was caused by a pipe bomb.
"Police are not ruling out anything including (Thai) politics and the conflict of ethnic Uighurs who, before this, Thailand sent back to China," Somyot said.
Thailand forcibly returned 109 Uighurs to China last month.
Hundreds, possibly thousands, of the Turkic-speaking and largely Muslim minority have fled unrest in China's western Xinjiang region, where hundreds of people have been killed, prompting a crackdown by Chinese authorities. Many Uighurs have travelled through Southeast Asia to Turkey.
The Erawan shrine, on a busy corner near top hotels, shopping centres, offices and a hospital, is a major attraction, especially for visitors from East Asia, including China. Many Thais also worship there.
Four Chinese, including two people from Hong Kong, were among the dead, China's official Xinhua news agency said. Two Malaysians, a Singaporean, an Indonesian and a Filipino were also killed, officials said. Scores of people were wounded, including many from China and Taiwan.
Thailand has been riven for a decade by a sometimes violent struggle for power between political factions in Bangkok.
An expert cleans an altar with a statue of Hindu god Brahma at the Erawan shrine, the site of a deadly blast, in central Bangkok, Thailand, August 18, 2015. Photo: Reuters/Athit Perawongmetha
Occasional small blasts have been blamed on one side or the other. Two pipe bombs exploded outside a shopping mall in the same area in February, but caused little damage.
Thai forces are also fighting a low-level Muslim insurgency in the predominantly Buddhist country's south, but those rebels have rarely launched attacks outside their heartland.
"This does not match with incidents in southern Thailand. The type of bomb used is also not in keeping with the south," army chief and deputy defence minister General Udomdej Sitabutr said in a televised interview.
Tourism is one of the few bright spots in an economy that is still struggling, more than a year after the military seized power in May 2014.
It accounts for about 10 percent of the economy and the government had been banking on a record number of visitors this year following a sharp fall in 2014 because of protests and the coup.
In Washington, the U.S. State Department said it was too soon to tell if the blast was a terrorist