Thai police say at least 28 people have been wounded by an explosion that went off in Bangkok during a march of anti-government protesters led by opposition leader Suthep Thaugsuban.
Authorities say the blast occurred after 1 p.m. in the capital on Friday. Television footage showed several protesters covered in blood, but here have been no reports of deaths.
Protesters were seen searching nearby buildings for the unidentified attackers, while ambulances rushed the wounded away. Police say the explosive device was thrown at the marchers.
There has recently been a series of drive-by shootings that protesters blame on the government.
Protest leader Suthep, who was not hurt by Friday's blast, is calling for an unelected people's council to replace the current government, which he says is corrupt and engages in nepotism.
Prime Minister Yingluck Shinawatra refuses to step down. She insists on holding early elections on February 2, though the opposition has said it will boycott the polls.
Until this attack, this week's protests have been peaceful, as police have largely stayed away and avoided conflict. But the protesters have also not been successful at shutting the government down as they had planned.
Thailand has experienced regular political turmoil in recent years. The conflict pits Bangkok's urban middle class and royalist elite against the mostly poor, rural supporters of Ms. Yingluck and her brother, former prime minister Thaksin Shinawatra.
Mr. Thaksin, who was ousted in a 2006 military coup, remains very influential in Thailand, even though he was convicted of corruption and lives in self-imposed exile.
Ms. Yingluck's Pheu Thai party is expected to easily win the February vote, thanks to the popularity of her brother, who remains popular in part because of social welfare programs he enacted.