A improvised explosive device fastened to a utility pole in front of the Erawan shrine at the Ratchaprasong intersection detonated at 6.55pm with a motorbike bomb in the intersection itself shortly after, causing two nearby taxis to explode. Body parts were scattered across the area, with only the smouldering wreckage of burned out motorcycles and cars left behind.
Military and police, including national police chief Somyot Pumpanmuang, rushed to the scene and two more devices, one found attached to a support pillar for the BTS Skytrain, were found in the hour after the first explosions. Military explosive ordnance disposal technicians defused both without incident.
Despite earlier reports the bomb at the BTS in front of Gaysorn Plaza prompted the transit system's closure, the Skytrain remained operational. Only the Ratchprasong Skywalk was closed. Rumours that Prime Minister Prayut Chan-o-cha had declared a state of emergency and ordered schools and businesses closed Tuesday were declared false and a hoax.
The Bank of Thailand also denied rumour it would call a bank holiday on Tuesday, according to Ronadol Numnonda, Assistant Governor of the Supervision Group.
Deputy Prime Minister and Defence Minister Prawit Wongsuwan expressed condolences to the families of the dead and injured victims. He said it was too soon to say if the attacks were politically motivated or terrorism.
"But it was clear that the perpetrators intended to destroy the economy and tourism, because it occurred in the heart of (Bangkok's) business district," Gen Prawit said, condemning the act.
It was clear, he said, human casualties were the goal of the attack.
Police said the IED that exploded inside the shrine area was composed of five kilogrammes of TNT. Authorities quickly recovered an electronic circuit suspected to be part of the device about 30 metres from the blast scene.
The force of the bomb was said to be intense, with reporters on the scene likening it to Iraq or Afghanistan. The iron fence surrounding the shrine was bent outward by the force of the blast.
Purported video of the blast from CCTV cameras was posted to Facebook after 8pm.
Most of those injured in the explosion were said to be predominantly Asian tourists, with the majority taken to Police General Hospital and Chulalongkorn Memorial Hospital, both of which were appealing for blood by 8.45pm.
Both hospitals also were calling for Chinese translators, as many mainland tourists were among the injured. The Japanese embassy said it is rushing to confirm whether any Japanese were caught in the blast.
Security officials cordoned off the bomb site for a radius of 200-300 metres to facilitate investigation. Police said the area has been cleared of bombs, but will remain off limits to the public.
Authorities have begun checking several other high-risk locations in Bangkok including Silom, Pathumwan, Thong Lor and Sukhumvit Road.
The Hindu Erawan shrine, on a busy corner near top hotels, shopping centres and offices, is a major tourist attraction, especially for visitors from East Asia. Many ordinary Thais also worship there.
Government and military officials so far have refused to speculate on whether Monday's bombing was political or tied to the ongoing unrest in the country's three southernmost provinces.
The Ratchprasong intersection where it is located has been the site of massive political protests in the past decade and a target for bombers. Bombs on the Ratchprasong Skywalk outside the nearby Siam Paragon shopping mall last year were believed to be poitically motivated, but remain unsolved.
Vehicle bombs, however, have been virtually unknown in Bangkok but have been a key weapon used by southern insurgents, as are the type of IEDs used inside the Erawan shrine complex.