Police on Tuesday used water cannon to fire tear gas solution at demonstrators trying to cut through razor wire erected outside parliament, and at least 18 people were hurt in the most violent confrontation since a youth-led protest movement emerged in July.
A group of demonstrators wearing helmets and other protective gear reached the line of concrete barriers and razor wire placed in front of the parliament in Dusit district at about 2.30pm. They then attempted to cross the barriers, throwing smoke bombs and bags of paint at riot police on the other side.
Police used water cannon to force them back.
The first three rounds consisted of plain water. When that failed to stop the demonstrators, police then used the water cannon to fire a liquid that included tear gas.
Ambulances took the injured to hospital. Bangkok's Erawan Medical Centre said 18 people were hurt, 12 of them suffering as a result of tear gas. It said one of those hurt was a police officer.
"This is brutal," said a 31-year-old volunteer with the FreeYouth protest group.
Protesters pushed forward behind makeshift shields - including inflatable pool ducks.
Some protesters scuffled with dozens of yellow-shirted royalists after an earlier rally by hundreds of right-wing Thais calling on lawmakers not to make changes to the constitution.
Pro-democracy leaders earlier announced a plan to stay overnight at the parliament while waiting for MPs to accept a proposed constitution amendment draft by civil group Internet Law Reform Dialogue (iLaw). It was one of seven drafts submitted to the parliament, with others sponsored by government and opposition parties.
Lawmakers are expected to discuss the issue for two days before voting on whether to accept any of the proposed drafts for deliberation.
