Thai democracy activists vowed Tuesday to return to the streets after police fired water cannon and tear gas on demonstrators in the most violent clashes seen since the protest movement erupted in July.
Forty-one people were injured as protesters forced through police barricades towards parliament in Bangkok, where lawmakers were debating possible changes to the military-scripted constitution.
Student-led rallies have rocked Thailand for months, demanding a constitutional overhaul and the removal of Prime Minister Prayut Chan-O-Cha, who took power in a 2014 coup.
Some in the movement have also called for reforms to the monarchy -- a once-taboo subject -- sending shockwaves through the Thai establishment.
Tuesday's demonstrations, with stone-throwing clashes between pro-democracy and hardline royalist protesters, saw a marked rise in violence.
Prominent student leader Parit "Penguin" Chiwarak called off the rally around 9pm (1300 GMT), urging protesters to regroup at a major intersection in Bangkok's shopping district on Wednesday afternoon.
"We will no longer be dust on anyone's feet," he said, wearing a bulletproof vest and speaking with a megaphone from a truck.
"Tomorrow we will open a new era in our fighting at Ratchaprasong. It is useless to stay because the chicken MPs and senators have fled the parliament."
According to the Erawan Emergency Medical Centre, 41 people were hurt in the protests, including five with gunshot injuries. They are receiving treatment at five hospitals.
A Bangkok police spokesman denied officers had used rubber bullets or live rounds in the operation.
- 'If we burn, you burn' -
Earlier protesters and police were locked in tense standoffs as night fell, though the mood calmed when demonstrators reached the main gates of the parliament, where they sat down to listen to speeches by their leaders.
The United Front of Thammasat and Demonstration student protest group later warned on social media: "If we burn, you burn with us."
Several thousand democracy activists massed in the afternoon near parliament -- where riot police had blocked off roads with barriers and barbed wire -- hoping to make their voices heard by lawmakers.
Police fired water cannon at protesters trying to dismantle a barricade, using water laced with irritant, sending demonstrators scrambling to wash their eyes.
Some sheltered behind giant inflatable rubber ducks which protesters had planned to float along the river behind parliament as lawmakers debated inside.
A police retreat at one barricade saw the first major scuffles between pro-democracy protesters and yellow-shirted ultra-royalist supporters, who threw bottles, rocks and rubbish at each other.
The confrontation initially looked like it would come to a peaceful end when a handful of people on both sides stopped to hug each other, but the bonhomie was short lived.
- Call for calm -
As police and protesters clashed outside, lawmakers were considering whether to debate seven possible constitutional amendments.
They include a proposal to replace the present military appointments in the Senate with directly elected representatives.
Parliament is expected to vote on Wednesday on which constitutional amendments bills will be debated.
But any constitutional change in Thailand is expected to take a long time and the junta-appointed Senate is unlikely to vote itself out of power.
Several opposition lawmakers came out of parliament to monitor police tactics.
Taopipop Limjittrakorn, an MP from the pro-reform Move Forward Party said police had been ignoring pleas to de-escalate the situation.
"Police should not be overly violent and threaten" protesters, he told reporters.
The royalists, who were permitted to rally in the parliamentary zone in the morning, are strongly opposed to all proposals to change Thailand's 2017 constitution, saying they would undermine the monarchy.
King Maha Vajiralongkorn sits at the apex of Thai power, supported by an arch-royalist military and the kingdom's billionaire clans.
The royal family enjoys support from mostly older conservatives and Thailand's monarchy is protected by one of the world's toughest royal defamation laws.
The ultra-wealthy monarch spends much of his time in Europe, but he has remained in Bangkok for the past few weeks.