Wu'er Kaixi, a former student leader of the 1989 Tiananmen Square pro-democracy movement, has announced he would run in a legislative by-election in Taiwan.

Wu'er, who has been living in exile in Taiwan since 1996 and obtained the self-ruled island's citizenship in 1997, said in a statement posted on his Facebook account early on Monday that he would contest the election in the central city of Taichung.

The seat had been vacated by Lin Chia-lung, an opposition politician who quit the post days before winning Taichung's mayoral seat in last weekend's local elections in which the China-friendly ruling Kuomintang suffered historic losses.

"It's glorious to step out at this historic moment," Wu'er said in his statement.

"From the Sunflower Movement to last weekend's elections, we can see that Taiwan has entered a new era. I call it Democracy 2.0," he said, referring to a student campaign in March protesting against a cross-strait services trade liberalisation pact pushed by the KMT administration and Beijing.

"I'm willing to enter parliament and become a pioneer of this new era."

Wu'er fled China for the United States initially after being named as one of China's most-wanted fugitives for his role in the 1989 demonstrations, which ended following a military crackdown on June 4, 1989.

China regards Taiwan as a breakaway province and has not ruled out the use of force to bring it back to its fold should the island declares independence.