Yang Chih-yuen, a Taiwan resident suspected of engaging in separatist "Taiwan independence "activities and endangering national security, has been under surveillance at a designated residence since Aug 4 after being apprehended by the Wenzhou State Security Bureau in Wenzhou, Zhejiang province.

On Aug 3, the bureau summoned the suspect, and placed him under surveillance the following day, China Central Television reported on Wednesday.

Yang's family have been informed about the changes in surveillance measures in line with the law, CCTV said, with more details of the man's secessionist activities being revealed.

According to the details disclosed so far, Yang, who was born in 1990 and is from Taichung, Taiwan, has long been poisoned by thoughts of "Taiwan independence" and began to engage in separatist activities when he was a middle school student in 2006.

He was selected by Taiwan's Democratic Progressive Party as a target to cultivate due to his active involvement in the "Wild Strawberries Movement", a protest on the island in 2008, CCTV said.

He was later named head of the DPP Youth League in Taichung and became a key member of the "Taiwan independence" separatist forces, the station added.

In 2011, Yang helped establish the "Taiwanese National Party", taking the initiative to plan and implement a series of secessionist activities in an attempt to build "a state through referendum", CCTV said.

After becoming vice-chairman of the "Taiwanese National Party "he began to handle the party's affairs as acting chairman in 2019 and to push "Taiwan independence" and promote the idea of independence in the shortest time more aggressively and hastily.

That same year, Yang was asked by Chen Shui-bian, the former Taiwan regional leader and secessionist, to represent the "Taiwan Action Party Alliance" during the election of a "legislator" for Yonghe district in New Taipei city, Taiwan. During the election, Yang advocated for "Taiwan independence" and incited confrontations between the island and the mainland, CCTV said.

Additionally, Yang colluded with separatist forces to support Hong Kong secessionists and incited secessionist forces to work together during the turbulence over the city's national security amendment bill in 2019.

The case against Yang is still underway, with a further investigation being conducted by the national security bureau in Wenzhou, CCTV added.

The news of Yang's capture came after a spokesperson for the Taiwan Work Office of the Communist Party of China Central Committee made remarks on Aug 3 about punishing die-hard "Taiwan independence" separatists.

Tang Yonghong, deputy director of the Taiwan Research Center at Xiamen University in Fujian province, welcomed the mainland's punishment of "Taiwan independence" secessionists on his account on Sina Weibo, China's Twitter-like platform, on Wednesday.

"Yang's case shows that the mainland has begun pursuing accountability for 'Taiwan independence' secessionists, and also indicates that the mainland has started to exercise legal jurisdiction over the island," he said in his post.

State security departments will use legal means, such as the Anti-Secession Law and the National Security Law, to severely punish those who resist reunification, seek independence, undermine peace or curb development, he said.

"It is likely that Yang will be the first secessionist to be held accountable, but by no means the last," he added.