A bomb planted at one of the Thai capital's most renowned shrines on Monday killed 16 people, including three foreign tourists, and wounded scores in an attack the government called a bid to destroy the economy.
There was no immediate claim of responsibility for the blast at the Erawan shrine at a major city-center intersection. Thai forces are fighting a low-level Muslim insurgency in the predominantly Buddhist country's south, but those rebels have rarely launched attacks outside their heartland.
"The perpetrators intended to destroy the economy and tourism, because the incident occurred in the heart of the tourism district," Defense Minister Prawit Wongsuwan told Reuters.
Several media outlets had earlier reported that 27 people were killed but national police chief Somyot Poompanmuang told reporters the death toll was 16 in an attack he said was unprecedented in Thailand.
"It was a pipe bomb," Somyot said. "It was placed inside the Erawan shrine."
The shrine, on a busy corner near top hotels, shopping centers, offices and a hospital, is a major attraction, especially for visitors from East Asia, including China. Many ordinary Thais also worship there.
The government would set up a "war room" to coordinate the response to the blast, the Nation television channel quoted Prime Minister Prayuth Chan-ocha as saying.
Two people from China and one from the Philippines were among the dead, a tourist police officer said. A rescue agency said 81 people were wounded and media said most of them were from China and Taiwan.
"It was like a meat market," said Marko Cunningham, a New Zealand paramedic working with a Bangkok ambulance service, who said the blast had left a two-meter-wide (6-foot-) crater.
"There were bodies everywhere. Some were shredded. There were legs where heads were supposed to be. It was horrific," Cunningham said, adding that people several hundred meters away had been injured.
At the scene lay burned out motorcycles, with rubble from the shrine's wall and pools of blood on the street.
Earlier, authorities had ordered onlookers back, saying they were checking for a second bomb but police later said no other explosive devices were found.
Authorities stepped up security checks at some major city intersections and in tourist areas. The city's elevated railway, which passes over the scene, was operating normally.
While initial suspicion might fall on Muslim separatists in the south, Thailand has been riven for a decade by an intense and sometimes violent struggle for power between political factions in Bangkok.
Occasional small blasts have been blamed on one side or the other. Two pipe bombs exploded outside a luxury shopping mall in the same area in February, but caused little damage.
Police said that attack was aimed at raising tension when the city was under martial law.
The army has ruled Thailand since May 2014, when it ousted an elected government after months of at times violent anti-government protests.
The shrine intersection was the site of months of anti-government protests in 2010 by supporters of ousted former Prime Minister Thaksin Shinawatra. Dozens were killed in a military crackdown and a shopping center was set ablaze.