Thailand's Parliament on Monday postponed a joint session as thousands of anti-government protesters surrounded the building in a bid to unseat the administration, reported CNN.
Thousands of protesters march to Parliament in Bangkok on Monday.
Samart Kaewmeechai, the deputy house speaker, said the Monday meeting was canceled because members of Parliament could not access the building.
Thousands of protesters from the People's Alliance for Democracy marched to Parliament at sunrise in a rally billed as their final bid to oust the government. Protesters have been camped at the prime minister's office compound for three months.
The parliamentary session was not immediately rescheduled.
The demonstrators were flanked by their own guards, who were armed with poles, clubs and metal rods. Many protesters carried masks and swimming goggles to protect against tear gas, which police have said they would use to maintain order.
The demonstrators initially called the protest to block Parliament from debating a bill to rewrite the constitution. That contentious issue was dropped at the last minute and lawmakers will instead debate legislation related to an upcoming regional summit.
Protesters have occupied the grounds of the prime minister's office for three months in their effort to topple the government, which they allege is the puppet of former Prime Minister Thaksin Shinawatra.
They accuse Thaksin, who was ousted by a 2006 military coup, of corruption and abuse of power, and claim the constitution bill before the legislature would help him stage a comeback.
Thaksin is in exile, a fugitive from a two-year jail term imposed after he was convicted last month of violating a conflict of interest law.
"I'm very scared. But it is time that we win this," said a protester, Wimon Sricarak. "We have been attacked, our friends have died, and all because they want to protect Thaksin."
Two small blasts went off before dawn Monday near the offices of a key protest leader, said police Sgt. Theerapong Rakjit. Nobody was injured and the origin of the blast was not immediately known.
The last time the group marched on Parliament, police efforts to disperse them resulted in running street battles. Two people were killed in the Oct. 7 violence and hundreds injured.
The fracas also disturbed animals at Dusit Zoo across the road, and zookeepers were forced to comfort highly strung animals such as kangaroos.
On Sunday, kangaroos, wallabies and elephants were taken by their handlers to the far side of the zoo, where they would be more protected from any mayhem. Dusit Zoo director Kanchanachai Saenwong said that despite the confrontations in the area, there were no plans to relocate the zoo.
The Education Ministry ordered four public schools in the area closed.
Police said 2,400 policemen would be stationed outside Parliament, which is about half a mile from the prime minister's compound. "Police and soldiers will not be armed with lethal weapons, only shields and batons," government spokesman Nattawut Sai-gua told The Associated Press.
The protest alliance also says it is committed to nonviolence, though forays outside its stronghold are usually led by tough young men, who carry homemade weapons such as iron rods -- and in some cases handguns -- and who have won a reputation for aggressive behavior.
The alliance accused police of being behind an attack last week in which grenades killed two protesters during demonstrations at and near the occupied Government House. Authorities have denied the charge.
Protest leaders were calling for Sunday's rally to be their biggest ever, but the number that turned out appeared to be at most just one-quarter to one-third the 100,000 supporters protest spokesman Parnthep Wongpuapan said had been expected.
"It will be D-Day. This will be our final push to bring down the government," 64-year-old protester Chokchuang Chutinaton said.
The alliance's supporters are largely middle-class citizens, who say Thailand's electoral system is susceptible to vote-buying and argues the rural majority -- the Thaksin camp's power base -- is not sophisticated enough to cast ballots responsibly.
They propose replacing an elected Parliament with one that is mostly appointed, a move critics charge is meant to keep power in the hands of the educated, urban elite.