At least 16 people were injured in a blast Sunday in a central Bangkok shopping district where anti-government protesters were holding a rally, the Erawan emergency centre said on its website.
"Sixteen people have been reported injured," the centre said, after the blast outside a major supermarket in a popular downtown commercial district.
Police could not immediately confirm the cause of the blast.
Blood was splattered on the pavement as soldiers and police sealed the area off, according to an AFP photographer at the scene.
Rallies trying to topple Prime Minister Yingluck Shinawatra have been hit by several gun and grenade attacks by unidentified assailants.
The protesters have carried out a self-styled "shutdown" of the city, blocking several key intersections for weeks as they try to pressure the government to resign.
A five-year-old girl was killed and several people were critically wounded in a drive-by shooting of an anti-government rally late Saturday in eastern Thailand.
Tensions are high in the kingdom as protesters try to upend the crisis-hit government and replace it with an unelected "people's council" to carry out reforms to root out corruption and alleged vote-buying.
Clashes between protesters and police last week left five people dead — including a police officer — in Bangkok's historic centre, close to the famous Khaosan tourist
