BANGKOK: Huge crowds 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 unelected “people’s council” that would oversee reforms to curb the political dominance of her billionaire family and tackle a wider culture of money politics.

Tens or even hundreds of thousands of flag-waving protesters massed at key intersections in the city, setting up rally stages along with tents for sleeping and stalls offering free food.

The well-organized protest movement has vowed to occupy parts of the capital until Yingluck quits, threatening to disrupt a February election, which it fears will only return the Shinawatra clan to power.

In the eyes of the protesters, Yingluck is “no longer prime minister,” firebrand protest leader Suthep Thaugsuban told reporters while leading a march through the capital.

A hardcore faction of the movement has threatened to besiege the stock exchange and even air traffic control if Yingluck does not quit within days.

The government said it would invite all sides to a meeting on Wednesday to discuss the election commission’s proposal to postpone the February 2 election, although it looks unlikely to agree to the demonstrators’ demand for a delay of at least a year.

The International Crisis Group think-tank warned Monday of a “potentially catastrophic” situation if people are denied the chance to vote.

“As anti-government protesters intensify actions, the risk of violence across wide swathes of the country is growing and significant,” it said in a report.

Within hours of launching the shutdown, the movement succeeded in bringing widespread disruption to Bangkok’s central retail and hotel districts, large swathes of which were taken over by whistle-blowing demonstrators.

Many schools were closed and some residents stockpiled food and water, but the city of roughly 12 million people — which has grown accustomed to large political rallies in recent years — did not grind to a complete halt.

The city’s subway and skytrain were running as usual, shops and restaurants were open and demonstrators promised to leave a lane unblocked at each major intersection to allow ambulances and buses to pass.

While there was the usual Thai carnival atmosphere, protests in the kingdom have a history of suddenly turning bloody, often at night and sometimes involving unidentified gunmen seeking to incite violence.

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.