China claims self-ruled Taiwan as its territory and has vowed to seize it one day, by force if necessary.

The People's Court of Wenzhou in eastern China sentenced Yang Chih-yuan on August 26 to nine years in prison on secession charges, Chen Binhua, the spokesman for China's Taiwan Affairs Bureau, said on state broadcaster CCTV.

Yang is the leader of a minor political party advocating for Taiwan's formal independence and once ran unsuccessfully for the democratic island's parliament, according to Taiwanese media.

He was arrested in China in 2022.

Chen said Yang had "conspired for the creation of a Taiwan state" in order to "undermine national unity" between 2008 and 2020.

He said Yang's conviction and sentencing were justified because he had played a "key role" in several organisations and because of the "malicious nature" of his activism.

Taiwan has been critical of Yang's treatment by China and condemned the accusations when he was charged in April as a rights violation meant to "create fear".

Beijing published judicial guidelines in June on criminal punishments for supporters of Taiwanese independence, including the death penalty for "particularly serious" cases involving "diehard" advocates.