Tens of thousands of protesters, many dressed in red to show their anger, demanded Tuesday that Taiwan's president step down over a series of corruption allegations.

President Chen Shui-bian called for unity, even as an opposition lawmaker scuffled with security guards while trying to confront the Taiwanese leader during a speech for National Day, which marks the establishment of China's first republic in 1911.

Chen told officials at an earlier ceremony he would not permit corruption to sully his administration.

"I myself have always insisted on clean politics," Chen said. "No one is above the law, even the president and his family. There are no exceptions."

Organizers of the anti-Chen campaign had pledged to bring 2 million people to the streets of Taipei for National Day celebrations.

Police estimated 125,000 protesters took part in a march in the area around the Presidential Office building during Chen's speech, while organizers said they had mobilized more than 1.5 million people.

Many were wearing red — symbolizing their anger with Chen's leadership.

About 5,000 police officers were on hand to maintain order. A few minor incidents were reported but there were no injuries.

Chen has been on the defensive for six months against allegations that his family and members of his inner circle used their connections to him for personal financial gain. Chen says he is innocent and will complete his remaining 19 months in office.

Last week, prosecutors cleared first lady Wu Shu-chen of involvement in a business scandal, citing a lack of evidence that she tried to influence a department store's takeover bid in return for favors.

Investigators are still looking into allegations that Chen misused secret diplomatic funds and are expected to close the probe by the end of October.

The Nationalist Chinese government resettled in Taiwan in 1949 after losing a civil war to Mao Zedong's forces on the mainland.