Two people were wounded Tuesday during an attack on a protest site in the Thai capital, which has seen an increase in violence amid a prolonged political standoff.
Thai officials said gunfire broke out in the early morning hours near an anti-government rally camp on the edge of Bangkok's Lumpini Park. Authorities do not know who was responsible.
Officials said there were also gunshots at a protest site in an upscale shopping district.
The violence comes after a series of bombings and shootings at anti-government demonstrations killed four people, including three children, and wounded dozens on Saturday and Sunday.
At least 20 people have been killed since November in the country's worst political violence since 2010, amid opposition efforts to oust Prime Minister Yingluck Shinawatra.
Some fear the unrest could get worse if the Red Shirt supporters of Yingluck take to the streets, as they have promised, to defend the government.
Prime Minister Yingluck's opponents contend her government is corrupt and controlled by her billionaire brother, exiled ex-prime minister Thaksin Shinawatra. They want her to step down and hand power to an unelected people's council.
Yingluck tried to resolve the conflict with early elections this month, but the opposition boycotted the vote and disrupted it in several areas, preventing a definitive result until more polls can be held.