Tens of thousands of Thai opposition protesters occupied major streets in central Bangkok on Monday in an attempted "shutdown" of the capital, escalating a campaign to unseat the embattled premier.
The demonstrators want Prime Minister Yingluck Shinawatra to resign to make way for an appointed government that would oversee electoral reforms to curb the political dominance of her billionaire family and tackle a wider culture of money politics.
Thousands of flag-waving protesters, some wearing T-shirts with slogans such as "Bangkok Shutdown" and "Thai Uprising 2014", massed at key intersections in the city, including outside a major shopping mall that was set on fire during deadly political unrest in 2010.
The protesters have vowed to occupy parts of the capital until they win their fight. They have vowed to disrupt a February election, saying it will only return Thaksin's allies to power without reforms first.
A hardcore faction of the anti-government movement has also threatened to besiege the stock exchange and even the kingdom's air traffic control if Yingluck does not step down within days.
"It's going to be very volatile," warned Pavin Chachavalpongpun, a former Thai diplomat and associate professor at the Centre for Southeast Asian Studies at Japan's Kyoto University.
"In a way there is no turning back for the protesters -- they have come too far," he added.
The protests are the latest chapter in a years-old political crisis that has gripped Thailand since Yingluck's older brother, fugitive former premier Thaksin Shinawatra, was ousted by royalist generals in 2006.
The protests were initially triggered by a failed amnesty bill that could have allowed Thaksin to return from self exile without going to jail.
The billionaire tycoon-turned-politician, who lives abroad to avoid a jail term for corruption, has strong electoral support in northern Thailand, but he is reviled by many southerners, Bangkok's middle class and members of the royalist establishment.
The turmoil comes as the country quietly braces for the end of revered but ailing King Bhumibol Adulyadej's more than six-decade reign.
The demonstrators say they want to rid Thailand of the "Thaksin regime", but deny accusations they are seeking to provoke another military coup.
"This is a people's revolution," said protest leader Suthep Thaugsuban, who faces a murder charge in connection with a deadly military crackdown on mass political rallies when he was deputy premier in 2010.
In the eyes of the protesters, Yingluck is "no longer prime minister", he told reporters while leading a huge crowd of supporters on a march through the capital.
Authorities say they are ready to declare a state of emergency if there is fresh unrest, and roughly 20,000 police and soldiers were due to be deployed for security, although there was little sign of them on the streets.
The government has not tried to stop the demonstrators taking over parts of the city, and Suthep has promised to retreat if the protests descend into "civil war".
Some local residents voiced fears that the action would hurt their livelihoods, particularly if tourists stay away during what is usually peak season.
"Of course it affects me -- I'm very stressed," said hair salon owner Tong, 69. "No customers are coming now as my regular customers cannot drive here."
Eight people, including a policeman, have been killed and dozens injured in street violence since the protests began over two months ago.
Fanning tensions, several shots were fired in a drive-by shooting at the headquarters of the opposition Democrat Party early Monday, while elsewhere a protest security guard was shot and wounded in a quarrel, police said.
The civil strife is the worst since 2010, when more than 90 people were killed in street clashes between pro-Thaksin protesters and armed soldiers.
The military -- traditionally a staunch supporter of the anti-Thaksin establishment -- has said it will not move to break up the latest protests.
"We will not use force to crack down. We will stand with the people," regional army commander Lieutenant General Theerachai Nakvanich, whose division covers Bangkok, told reporters.
Police said there were 12 hospitals, 28 hotels, 24 schools and five fire stations within the areas affected by the shutdown.
Most people appeared to have opted to leave their cars at home and rely on public transport instead.
The shutdown has sparked panic buying among some residents and the US embassy has advised stockpiling a two weeks' supply of food, water and medicine.
Smaller rallies have been held in the capital to back the February election and oppose the shutdown, while government supporters planned to gather in various locations in northern Thailand on Monday.