Hundreds of thousands of protesters are expected to gather in Taipei today for a rally against embattled "president" Chen Shui-bian, which will clash with the island's "national day" celebrations.

Organizers said they expected as many as 2 million people to protest in the square outside the "presidential" office, where the major celebrations have also been scheduled.

"As Chen is the 'head of the state,' he will have to show up during the celebrations," campaign spokesman Emile Sheng said. "And certainly there won't be a better chance than this for the people to voice their anger towards Chen Shui-bian."

Protesters were asked to wear red in a show of anger over the string of high-profile corruption scandals implicating Chen and his family.

Chen's office urged people not to interrupt the celebrations, a move it said would otherwise tarnish the island's image.

Campaign organizers said they had advised protesters against disrupting the celebrations, which include an honour guard parade and are expected to draw large crowds.

"Our target is Chen Shui-bian rather than the 'national day' celebrations," Sheng said.

About 5,000 police are expected to patrol the square, and campaign organizers have been asked to carry radios to ensure that communication and order are maintained during the protest, which will be restricted to a designated area.

"Premier" Su Tseng-chang said the rally was illegal, as the organizers had not secured approval from the authorities, but did not urge people to stay away.

Shih Ming-teh, a former Chen ally and also former chairman of Chen's ruling Democratic Progressive Party (DPP), started an island-wide protest tour late last month to solicit more support for his campaign. The tour ended late on Saturday in central Taichung.

Pressure has mounted on Chen to resign after he was questioned 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.

On Friday, Taiwan's "parliament" will vote on a second recall motion launched against Chen by the opposition People First Party (PFP).

Observers said the motion, which requires the backing of 148 "lawmakers," is unlikely to pass as the PFP and its Kuomintang ally hold only 112 seats.

Against this backdrop, activists announced on Sunday they were widening their campaign to target "lawmakers" from Chen's DPP.