TAIPEI: A month-long campaign to oust Taiwan's embattled "president" Chen Shui-bian reached a climax yesterday as more than 1.5 million people gathered in Taipei to demand Chen's resignation for alleged corruption, organizers said.

As Chen spoke at a "national day" celebration ceremony, about 50 "legislators" from the main opposition Kuomintang (KMT) party who had been invited onto the stage shouted "Down with A-Bian," using his nickname, and made the thumbs-down gesture.

Scuffles between members of Chen's Democratic Progressive Party (DPP) and the KMT broke out when security officers removed the opposition "legislators" from the stage as they unfurled red banners accusing Chen of corruption and urging him to resign.

Several blocks away, hundreds of thousands of people, most wearing red shirts and hats to symbolize their opposition to Chen, rallied to demand he step down over a string of corruption scandals that have embroiled him and his family in recent months.

"A-Bian Out," they roared.

The month-long anti-Chen campaign was launched by Shih Ming-teh, Chen's former ally and former DPP chairman.

"Chen Shui-bian must respond to the demands of the people," Shih told supporters.

Barbed wire barricades erected by police prevented the protesters from approaching the "presidential" complex.

Shih said the crowd which fanned out to fill boulevards leading from all directions to the "presidential" square "exceeded 1.5 million" in a campaign that aims to "lay siege" to Chen's office.

Organizers had pledged to bring 2 million people to the streets around the "presidential" office, but police estimated 125,000 protesters took part in the march. About 15,000 police and security officers were mobilized to maintain order.

KMT Chairman Ma Ying-jeou said Chen should listen to the protesters.

"Now that over 60 per cent of Taiwanese believe he's unfit to serve as 'president,' he must not continue to play dumb."

Pressure has mounted on Chen to step down after he was questioned in August over alleged misuse of funds intended for "state" affairs. He has denied any wrongdoing and vowed to stay on until his second and final term ends in May 2008.

Prosecutors said last week that Chen's wife, Wu Shu-chen, did receive and spend about NT$300,000 (US$9,090) worth of department store vouchers which were alleged to be gifts in exchange for lobbying favours but said they would not prosecute her for lack of evidence. Their son-in-law, Chao Chien-ming, was indicted on July 10 on an insider trading charge. The case has not been resolved.