TAIPEI (Taiwan News) — A Taiwanese citizen, held in China since 2018, was handed a second sentence of four years in prison by Chinese authorities this week, who allege that he worked as a spy for Taiwan.

China’s Taiwan Affairs Office (TAO) announced the additional sentence for Tsai Chin-shu (蔡金樹) at a press conference on Wednesday (Sept. 27). This comes after Tsai, a pro-unification scholar, completed an initial four-year prison sentence in May.

A July 2023 report from LTN indicated that Tsai already served one four-year sentence and had his rights in China revoked for an additional four years, making him unable to leave the country despite his release. Since May, Tsai’s movements have been restricted to a residence on Xiamen’s Gulangyu Island, per LTN.

Tsai was one of four Taiwanese men charged with espionage and “threatening national security” by Chinese authorities in October 2020. All four of the alleged spies had recorded “confessions” publically aired on Chinese state-run media at the time.

After the new sentence handed down this week, Tsai will return to a Chinese prison for another four years. Tsai’s alleged “confession” from 2020 indicates he was gathering intelligence for the Taiwan Military Intelligence Bureau.

Tsai is a scholar of political science and the former chairman of the South Taiwan Cross-Strait Relations Association, an organization promoting unification with China. Before 2018, he made frequent trips between Taiwan and China for business and academic exchanges.

The four alleged spies are all China-friendly academics, and all faced charges similar to Tsai. They include Tony Shih (施正屏), Lee Meng-chu (李孟居), and Cheng Yu-chin (鄭宇欽).