Through the afternoon, police fired teargas on stone-throwing protesters in chaotic demonstrations that paralysed parts of Bangkok and followed a night of gun and knife battles during which two people were killed and at least 54 wounded.
A group of protesters forced Prime Minister Yingluck Shinawatra to evacuate to an undisclosed location from a building where she had planned to give media interviews, while hundreds seized control of state broadcaster Thai PBS, waving flags, tooting whistles.
Declaring Sunday "V-Day" in a week-long bid to topple Yingluck and end her family's more than decade-long influence over Thai politics, protest leaders urged supporters to seize 10 government offices, six television stations, police headquarters and the prime minister's offices in what they are calling a "people's coup".
Police said about 30 000 anti-government protesters had gathered in at least eight locations. In three of them, police used teargas and water canon against people hurling stones, plastic water bottles and other projectiles.
"Police and protesters still haven't come face to face. The use of teargas is part of our procedures," national police spokesperson Piya Utayo said on television.
It is the latest dramatic turn in a conflict pitting Bangkok's urban middle class and royalist elite against the mostly rural poor supporters of Yingluck and her billionaire brother, Thaksin Shinawatra, a former prime minister ousted in a 2006 military coup.
Reuters journalists waiting to interview Yingluck inside the police Narcotics Suppression Bureau were told by Natthriya Thaweevong, an aide for the prime minister, that she had left after protesters made it inside the outer part of the compound, the Police Sports Club, where the bureau is located.
In another area of the city, outside the Metropolitan Police Bureau, about 3 000 protesters rallied, accusing riot-clad police of being manipulated by Thaksin, a former policeman who rose to become a telecommunications magnate before entering politics and winning back-to-back elections in 2001 and 2005.
Chamai Maruchet Bridge, north of Government House, the prime minister's offices, was a scene of nearly non-sop skirmishes, as police repeatedly fired teargas into the stone-throwing crowd, Reuters witnesses said. Protesters gathered near barricades spray-painted with the words "Failed State".
In one of the most dramatic events, state broadcaster Thai PBS was taken over by protesters, according to PBS and police. More than 250 mostly black-shirted protesters gathered in the parking lot, as others streamed in.
The executive producer at Thai PBS, Surachai Pannoi, told Reuters the management of the station would share its broadcast line with Blue Sky, a broadcaster controlled by the opposition Democrat Party, starting this afternoon.
Across Bangkok, police tightened security after clashes erupted on Saturday night between supporters and opponents of Yingluck near a sports stadium where about 70 000, red-shirted government supporters had gathered. Five major shopping malls closed their doors across Bangkok, underscoring the widening economic impact of the protests.
One "red shirt" government supporter was shot and killed outside the stadium early on Sunday, after a 21-year-old student was fatally shot several hours earlier.
Streets near the stadium, the scene of battles overnight, were littered with broken glass and rocks, a Reuters witness said. A red-shirt leader, Jatuporn Promphan, said four red shirts had been killed but Reuters only confirmed one, 43-year-old red-shirt guard Viroj Kemnak.
Fifty-four people were wounded in the fighting, according to the government's Erawan emergency centre.
Thousands of government supporters began to disperse, returning on buses to their homes in the north after their rally was called off in a bid to calm the tension.
But that is unlikely to end Thailand's worst political crisis since April-May 2010, a period of unrest that ended with a military crackdown. In all, 91 people were killed then, mostly Thaksin's supporters trying to oust the then government.
Economy at risk
Yingluck, who won a 2011 election by a landslide to become Thailand's first female prime minister, has called on the protesters to clear the streets and enter into talks, saying Thailand's economy was at risk after demonstrators occupied the Finance Ministry on Monday.
Protest leader Suthep Thaugsuban has ignored her and told demonstrators that laws must be broken to achieve their goals.
Seventeen battalions of 150 soldiers each, along with 180 military police, all unarmed, were called in to boost security on Sunday ahead of a deadline the same day set by demonstrators for ousting the government.
Fighting had intensified on Saturday after anti-government protesters attacked a bus they believed was full of government supporters. They also smashed the windshield of a taxi carrying people wearing red shirts, a pro-government symbol, and beat two people, one unconscious, police and witnesses said.
As darkness fell on Saturday, gunfire erupted outside the sports stadium in Bangkok's Ramkamhaeng area, where the backers of Yingluck and Thaksin had gathered for a show of support.
At around 8pm, a gunman fired into Ramkamhaeng University, where hundreds of anti-government protesters had retreated after trying to block people from entering the stadium, witnesses said. One person was killed. It was not known who fired the shots.
Fighting raged in the area through the night.
At around 2am, Kittisak Srisunthorn (36) said he was shot in the arm while sitting with a group of red-shirt guards.
"I heard homemade bombs, gunshots. People started to throw rocks and glass bottles. There were around 100 people gathered. I didn't see any police," Kittisak told Reuters.
Thaksin, who won over poor rural and urban voters with populist policies, was convicted of graft in 2008. He dismisses the charges as politically motivated. He remains in close touch with the government from his self-imposed exile, sometimes holding meetings with Yingluck's Cabinet by webcam. – Reuters