Shih Ming-teh, former chairman of the Democratic Progressive Party (DPP), led a long column of protesters wearing red T-shirts in a mid-day parade to Chen's downtown office. They shouted slogans while giving the thumbs-down sign which has become a trademark gesture of the protesters.

Taiwan media said a mass sit-in was scheduled to last until 9 p.m., but Shih said he would remain outside the downtown office, along with other willing protesters, until Chen quits.

Shih said on Saturday afternoon that the sit-in would last until Chen resigns. He's asked that the mass protest resume again at 3 p.m. Sunday.

"So many people are standing here today to demand Chen resign, which shows the people of Taiwan know the difference between right and wrong," said Shih.

"When Chen commits corruption, Taiwan people have the right to oust him," said Shih. He said if Chen refused to resign, Taiwan would be "paralyzed" and Chen would become a "prisoner" of his office.

Shih led people in chants of "Chen, step down" during his speech.

On Saturday afternoon, people formed a giant "totem" pattern -- a bow compass symbolizing rules. The pattern also looks like a warrior, with a broadsword in hand, cut down the corrupt regime, which represents humans beseeching power from heaven, according to a spokesman for the headquarters.

A Taiwan newspaper opinion poll found that 68.5 percent of Taiwan residents support the campaign to oust Chen Shui-bian.

On August 12, Shih Ming-teh launched the "one million people oust Chen Shui-bian" campaign to force the Taiwan leader to step down after some of his family members were implicated in a series of scandals.

Last week Chen admitted that he had used other people's receipts to write off his official expenses and that his family accepted free coupons from a local businessman to shop at the Sogo department store, according to media reports from Taiwan.