The arrest of Sun Wenguang, a retired professor from the Shandong province of northeastern China, during a live-telephone interview with VOA has come at a sensitive time when the rule of Chinese leader Xi Jinping is being seriously challenged.



Observers say that has led to the security apparatus' swift action in crushing the country's rising anti-government sentiments, which they see as a threat to the Communist Party's regime.



Three days after his "enforced disappearance," rights activists at home and abroad are demanding that China immediately release the 84-year-old professor for fear he may face physical torture, criminal charges or both.



FILE - Former professor Sun Wenguang speaks in his FILE - Former professor Sun Wenguang speaks in his home in Jinan, east China's Shandong province, Aug. 28, 2013. FILE - Former professor Sun Wenguang speaks in his home in Jinan, east China's Shandong province, Aug. 28, 2013.

They also are urging the international society to call for a systemic change of China's political and legal framework, in which they say the state is continuing to abuse its power and crack down on dissidents.



Nodes of independence in China



"It's absolutely part of the attempts under Xi Jinping to find every little node of independence in society and crush it," said Michael Caster, co-founder of Safeguard Defenders. Sun's arrest has to do with "the political situation in mainland China, including the image of Xi Jinping recently also being challenged by [those] both inside and outside [the] establishment.



That may also [pose] a security concern" to Chinese authorities, said Richard Tsoi, vice chairman of Hong Kong Alliance.



Caster added that Sun makes an obvious target under China's intensified crackdown on dissidents since he has had a long track record of being critical of the state and is a signatory of Charter 08 — a manifesto drafted by late Chinese Nobel Laureate Liu Xiaobo to advocate reforms that would result in a separation of powers, a new constitution and legislative democracy in China.



Speaking out



Critics have been emboldened by a recent vaccine scandal in China, a trade spat with the United States, and economic headwinds, and are openly questioning Xi's sweeping control. This includes Xu Zhangrun, a law professor from Tsinghua University, who has delivered what was believed to be the fiercest denunciation yet of Xi from a Chinese academic.



The New York Times reported on Wednesday that Xu "challenged political taboos" at a time when the voice of Chinese intellectuals is dying out.



Xu urged the Chinese government to overturn its condemnation of the pro-democracy Tiananmen protests in 1989, calling on Chinese lawmakers to reverse the vote that abolished a two-term limit on Xi's presidency.



Many are keeping an eye on how authorities will deal with Xu once he returns to China from Japan orwhether he will encourage others to speak out.



Relentless harassment



Prior to Xu, Sun has long been outspoken, which has made him a target of constant harassment by the communist government.



Earlier this year, Shandong University's Communist party chapter ruled to cut Sun's retirement pension by almost half for what it said were his subversive remarks, and it further threatened to eliminate altogether his pension if he continued to talk to foreign media.



Sun had been under intense scrutiny for some time, and security officers had staked out his apartment, keeping a tab on all of his movement.



Sources tell VOA's Mandarin service that Sun currently is being detained at Yanzi Mountain Villa at Jinan Military Region, a military-linked hotel and reception center.



Other details of his incarceration are unclear, and rights activists are concerned about what may be coming next for Sun.



"The legal system in China is serving purely to the will of the party, and so if they decide to conjugate some charges against him, then they will. Or they'll hold him for an indefinite period of time," Caster said.



He said Sun may share a fate similar to that of his one-time defender and legal counsel, Wang Quanzhang. Wang vanished more than three years ago and has not been heard from since, although he reportedly was seen in the Tianjin No. 1 Detention Center by a former colleague. Wang's wife has said reports are that her husband is alive in a decent physical and mental state.



Sun also may be forced into making a televised confession. A report from Safeguard Defenders concludes the state has grown heavily reliant on illegal forced confessions by detainees to denounce right activists and dissidents for both a domestic and international audience.



False charges



In addition, Sun could face charges of colluding with a foreign power, according to Hunan-based rights activist Ou Biaofeng.



"As a minimum, [he will be given] a warning or [put under] house arrest. Or the authorities may make up some false charges against him, for example, collusion with foreign hostile forces," Ou said, calling authorities in China "barbaric, ridiculous and evil" in suppressing the true voice of its citizens.



International rights groups, including Reporter Without Borders (RSF), have joined hands to throw support behind Sun and demand his immediate release.



"The professor is known for his assertive public interventions against censorship and propaganda. RSF demands his immediate release and stresses that freedom of speech and freedom of the press are explicitly written the Constitution of the People's Republic of China," its statement read.



"China may be richer, [but certainly not freer.] The regime has intensified its suppression on rights crusaders and dissidents by having lawyers arrested and using technologies to launch a full-scale surveillance on the public's freedom of speech online or offline. China has gone overboard," said Chiu Ee-ling, secretary-general of Taiwan Association for Human Rights.