TAIPEI, Taiwan (AP) — A Taiwanese pro-democracy activist who served five years in China returned to Taiwan on Friday morning, the island's Central News Agency reported.

Lee Ming-che was arrested by Chinese authorities in 2017 and charged with subversion of state power. His arrest was China’s first criminal prosecution of a nonprofit worker since Beijing passed a law tightening controls over foreign non-governmental organizations in 2016.

Lee had given online lectures on Taiwan’s democratization and managed a fund for families of political prisoners in China.

For the past five years, he served his sentence in a prison in central Hunan province. Lee arrived back in Taiwan Friday morning, flying from the southern Chinese city of Xiamen.

His arrest came after relations between China and Taiwan soured, after the island elected Tsai Ing-wen as president. Tsai's Democratic Progressive Party has advocated for Taiwan’s formal independence. China cut off contact with Taiwan’s government after Tsai came into office and now sends military planes flying towards the island on a daily basis.

China claims Taiwan is part of its national territory and claims Taiwanese nationals are also Chinese, issuing them a special identity card.