A bomb attack wounded dozens of people at an opposition protest march in Thailand's capital on Friday, sending tensions soaring following weeks of mass rallies aimed at overthrowing the government.
The kingdom has been periodically rocked by political bloodshed since former prime minister Thaksin Shinawatra was overthrown by royalist generals in a coup seven years ago.
His sister, Prime Minister Yingluck Shinawatra, has faced more than two months of street demonstrations aimed at forcing her government from office and installing an unelected "people's council."
The authorities and demonstrators both blamed each other for the blast, which was apparently caused by a grenade-type device thrown from a nearby building.
The anti-government movement said the explosion happened shortly before rally leader Suthep Thaugsuban was due to pass by.
"The bomb went off about 30 metres (100 feet) from Suthep," protest spokesman Akanat Promphan told AFP. "Then his bodyguards escorted him back to a rally stage."
Television footage showed several people lying on the ground as ambulances rushed away the wounded. Protesters were seen searching nearby buildings for the attackers.
The city's Erawan emergency centre said 36 people were hurt, including one who was undergoing an emergency operation.
Eight people have been killed and hundreds wounded in street violence since the protests began.
Yingluck's supporters fear the violence is aimed at provoking another military or judicial coup to remove her from power.
Demonstrators, backed by the country's royalist establishment, have occupied major intersections in the capital since Monday in what they have dubbed the "Bangkok shutdown".
There have been a series of night-time 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.
The latest blast raised the attacks to "a new level" as it happened in broad daylight and was "apparently intended to cause significant casualties", said Anthony Davis, a Thailand-based security analyst at IHS-Jane's.
"This a political situation in which extremists on both sides can flourish and it is not inconceivable that this could have been done by people who want to fan public anger at the government and reignite the whole protest movement," he told AFP, noting that turnout had fallen in recent days.
He was sceptical that the perpetrators hoped to unleash another military coup with Friday's blast alone.
"It's going to take more than this to have tanks rolling down the streets. My assessment is you would have to have bombs like this going off twice a day, a lot of blood on the streets and probably crowds clashing with each other before the army comes in and says game over."
The protests were triggered by a failed amnesty bill that could have allowed Thaksin to return without going to jail for a past corruption conviction.
The demonstrators accuse the billionaire telecoms tycoon-turned-politician of controlling his sister's government from his base in Dubai.
Thaksin has strong electoral support in northern Thailand, but he is reviled by many southerners, Bangkok's middle class and members of the royalist establishment.
Yingluck has called an election for February 2 in an effort to defuse the deepening crisis but the main opposition Democrat Party is boycotting the polls, which they fear will only return the Shinawatra family to power.
"I think the election will be the answer," Yingluck told foreign reporters on Friday before the blast, saying that her family was "one of the victims".
"We just do our job. So that is why (an) election will be the only way to clear out our family," she said.
The government has urged police to detain rally leader Suthep, who faces an insurrection charge -- in theory punishable by death -- in connection with the protests.
Yingluck is also facing several legal moves which experts say could potentially bring down her government.
On Thursday the National Anti-Corruption Commission launched an investigation into possible negligence of duty by Yingluck in connection with a controversial subsidy scheme for rice farmers.