The ruling Chinese Communist Party under President Xi Jinping has launched a crackdown on the families of overseas dissidents as part of a nationwide probe into an open letter calling on him to resign.
The authorities are already questioning a number of employees of the Watching News website after an open letter signed by "loyal party members" and accusing Xi of a major power grab that had damaged China's interests was published there, allegedly by hackers.
Now, police have detained three relatives of Germany-based journalist Chang Ping, who lost his job at a state-run newspaper in 2011, apparently in connection with the same investigation.
"My two brothers and my sister were kidnapped by police in China's Sichuan province on [Sunday]," Chang told RFA. "They were on their way back to our parental home to visit our ageing parents when they were detained."
"They were held against their will with no legal process whatsoever," he said.
Chang's relatives had been told by police to contact him and warn him off writing any more articles critical of the communist regime, he said.
"If they didn't, they said they would find a way to frame them for some crime," he said.
Chang said the threats seemed to be linked to the probe into the open letter to Xi.
"The government is very concerned about this, and they have set up a special task force to investigate," he said.
"But I have personally had nothing whatsoever to do with the drafting or publication of this letter."
In a longer statement translated by the U.S.-based website China Change, Chang vowed to continue with his work as before, adding that he would support his family if they chose to cut ties with him.
"The harassment and threats of the authorities allow me to see even more the value of my writings, and encourage me to work harder in future," wrote Chang, who has a regular column for Deutsche Welle.
The detention and threatening of Chang's relatives comes after New York-based blogger Wen Yunchao said his relatives were also targeted.
Wen, who writes under the pen-name Bei Feng, said on his Twitter feed that that his parents and younger brother were detained on March 22 in the southern province of Guangdong.
'Huge pressure' on family
Wen, whose friends say had merely retweeted the report on Watching News about the letter to Xi, said he believed his family’s disappearance was also related to the case.
But Wen declined to give an interview when contacted by RFA on Monday. "It's not convenient to speak to you because my family are really under huge pressure," he said.
Beijing-based rights activist Hu Jia said he was shocked at the lengths to which the authorities have gone in reaction to the letter.
"If I'd known about it, I would have signed it, even put my name to it as a co-author," Hu said. "Xi Jinping has presided over a brutal regime in recent years, both by jailing people, and by means of an unprecedented level of control on freedom of speech."
"He has done so many evil deeds, including the crackdown on lawyers and on citizens who supported [Hong Kong's pro-democracy] Umbrella movement, that he shouldn't just resign; he should stand trial," Hu said.
Germany-based journalist Su Yutong said she, like Chang, had been forced to leave China because of growing restriction on freedom of expression.
"I think that this open letter really shook them up in a big way, and that the situation looks really very frightening both for a lot of dissidents and for people who had nothing to do with it," Su said.
She said Chang, who has been targeted via his family in the past, is unable to return to China, while his family are unable to leave.
"The authorities will target the families of dissidents like us ... but we are doing these things out of personal choice, not because our parents told us to do them," Su said.
Earlier this month, police also detained journalist Jia Jia in connection with the open letter, but have since released him, his lawyer Yan Xin told Deutsche Welle.
Reported by Xin Lin for RFA's Mandarin Service, and by Wen Yuqing for the Cantonese Service. Translated and written in English by Luisetta Mudie.