Blast hits Thai anti-govt protest march

A bomb blast has struck an anti-government protest march in the Thai capital, wounding at least 28 people, officials say, sending tensions soaring following weeks of mass opposition rallies.

It is the latest in a series of attacks by unknown assailants against demonstrators seeking to oust Prime Minister Yingluck Shinawatra.

The protest movement said the blast happened shortly before rally leader Suthep Thaugsuban was due to march past the spot.

"The bomb went off about 30 metres from Suthep and then his bodyguards escorted him back to a rally stage," spokesman Akanat Promphan said.

Television footage showed several people lying on the ground as ambulances rushed away the wounded.

Protesters were seen searching nearby buildings for the attackers.

Police were investigating what type of explosive device caused the blast.

An official from the city's Erawan emergency centre said 28 people were hurt in the explosion, without giving details of the injuries.

Yingluck has faced more than two months of street demonstrations aimed at forcing her elected government from office and installing an appointed body to oversee loosely defined reforms such as an end to alleged vote buying.

Eight people have been killed and hundreds injured in street violence since the protests began.

There have been a series of drive-by shootings at rally sites and grenade attacks on the houses of opposition politicians that both the demonstrators and the government have blamed on each other.

"Yingluck must take responsibility," one of the protest leaders, Satit Wonghnongtaey, said on stage soon after the blast.

"This government, Yingluck and Red Shirt thugs are creating violence," he said, referring to a rival pro-government protest movement whose rallies in 2010 were suppressed in a bloody military crackdown.

The government denied the claim, saying the protesters were trying to incite violence.

"A movement has been set up to create a situation of bomb attacks against leaders' houses and protesters," Deputy Prime Minister Surapong Tovichakchaikul told reporters.

The opposition demonstrations aim to curb the political dominance of Yingluck's billionaire brother, fugitive former premier Thaksin Shinawatra, whom they accuse of controlling the government from self-exile.