Protesters throng downtown Bangkok
Thailand's capital has been the scene of similar demonstrations the last four weekends, but this was the most disruptive one of all.
Thousands of protesters — mainly poor, rural protesters known as the Red Shirts — staged a sit-in and vowed they won't leave until Prime Minister Abhisit Vejjajiva dissolves parliament and calls new elections.
Supporters of ex-Prime Minister Thaksin Shinawatra and pro-democracy activists are feeling emboldened after scoring a couple of victories since the protests began, observers say.
First they forced Abhisit to the negotiating table last weekend. They also won what they consider to be a major concession from him: he agreed there will be elections and that he will dissolve parliament before the end of the year.
But protesters, opposed to a 2006 military coup which ousted Thaksin, want Abhisit to resign and call elections immediately to ensure that Thailand once again has a democratically elected government.
Protesters expected to sit tight for weekend
The government first ordered them out before the end of the day but as the deadline passed said negotiations would continue Sunday.
In a video phone-in Saturday night, Thaksin repeated his calls for the protesters to stay the course.
"Fight and be tired for a few more days. This is better than being tired for the rest of your lives due to injustice," he said.
"I ask that those of you working the next few days to please take days off and join us here. Please be patient. Victory is just around the corner."
Protest leaders have portrayed the demonstrations as a struggle between Thailand's impoverished, mainly rural masses — who benefited from Thaksin policies of cheap health care and low-interest village loans — and a Bangkok-based elite seen as impervious to their plight.
Thaksin's allies won elections in December 2007, but two resulting governments were forced out by court rulings. A parliamentary vote brought Abhisit's party to power in December 2008.
The Red Shirts say his rule is undemocratic and that only new elections can restore integrity to Thai democracy.
With files from The Associated Press