Thai police fired tear-gas canisters at thousands of anti-government protesters Tuesday, some of whom barricaded Parliament to prevent lawmakers from entering, reported CNN.
Prime Minister Somchai Wongsawat, who was sworn in September 25, was scheduled to lay out his policy plan in his first speech to lawmakers.
Many parliamentarians were unable to make it inside the building because of the protesters and the presence of riot police.
Several others -- members of the opposition -- boycotted the speech.
Parliament eventually convened after a delay.
Paramedics said 75 protesters were hurt in the clashes. They expect the figure to go up as police try to disperse demonstrators who are trying to lay siege to other government buildings near the Parliament in the capital city, Bangkok.
Tuesday's flare-up is the latest in an ongoing crisis that has gripped the nation since summer when anti-government demonstrators, led by the People Alliance of Democracy (PAD), undertook efforts to purge the current Cabinet.
On Sunday, Thai police arrested a key opposition leader as part of its crackdown on the anti-government protests.
Chamlong Srimuang, a PAD leader, was arrested from a polling booth after he cast his ballot in the Bangkok's gubernatorial elections.
Since August 26, the PAD and its supporters have laid siege to the Government House -- the seat of the Thai government -- saying they will not leave until the ruling People Power Party (PPP) and its allies are ousted from office.
Police issued arrest warrants against Chamlong and nine other leaders, charging them with insurrection, conspiracy, illegal assembly and refusal to disperse.
On Friday, authorities took into custody another PAD leader, Chaiwat Sinsuwong.
The anti-government alliance accuses the PPP of being a proxy government for one-time Thai Prime Minister Thaksin Shinawatra, who was ousted in a bloodless coup in 2006.
Thaksin returned to Thailand after the PPP swept into power in December 2007, but fled again in August just as he was to appear in a corruption case against him.
The PAD contends that the People Power Party wants to amend the constitution so Thaksin does not have to face charges.
The protesters have held mass street demonstrations, some of which ended in clashes with pro-government supporters.
The protests began with the PAD calling for the ouster of Samak Sundaravej, who was then the Thai Prime Minister.
Samak was eventually removed from office after a constitutional court ruled on September 9 that he had violated the constitution by appearing as a paid guest on a TV cooking show.
But opposition party supporters were further inflamed when Samak was replaced by Somchai, Thaksin's brother-in-law.