Updated at 2.00 p.m. ET on 2014-4-29
The disappearance of veteran Chinese journalist Gao Yu sparked growing concerns on Tuesday, as authorities in Beijing tightened controls on dissidents and rights activists ahead of a sensitive anniversary.
Gao has been out of contact with family and friends since failing to show up at an event commemorating the 25th anniversary of the military crackdown on the 1989 student-led pro-democracy movement in Beijing on Saturday, her friends and lawyer said.
The event was to have marked the 25th anniversary of the "April 26 Editorial" in the ruling Chinese Communist Party's People's Daily newspaper that called the protests in Tiananmen Square "an anti-party and anti-socialist upheaval."
Yao Jianfu, Gao's friend and former research official at China's cabinet, the State Council, said he had already lodged an official inquiry about her whereabouts, but had met with no response.
"The police officer on duty said they didn't know [where she is], and another police officer said they would get back to me if they got any information," Yao said in an interview on Tuesday.
"But neither the citizens' affairs bureau nor the police have answered my question up until now."
Beijing-based rights activist Hu Jia said he was unable to figure out the reason for her disappearance.
"All those times I was put under house arrest, she wasn't," Hu said. "Recently, she attended the memorial event for [late former premier] Hu Yaobang on April 15."
"I think the authorities have either implemented a forced disappearance or criminal detention," he said. "But from where I'm sitting, it's hard to see what the reason might be."
No 'sensitive' writing
He said Gao, who frequently gave outspoken interviews to overseas media, and who also worked for Germany's Deutsche Welle radio service, hadn't written anything particularly sensitive.
"Her recent articles didn't contain anything that could be considered a state secret or anything, I don't think," Hu said.
Bob Dietz, Asia program coordinator at the New York-based Committee to Protect Journalists (CPJ), wrote in a blog post that Gao's "normally active" Twitter feed has seen no new posts since April 23.
"It has been a government tradition to start cracking down on protesters, critics, and dissidents before April 15, and this year is no different," Dietz said.
"China watchers say the strictures have already begun with warnings to some and detentions for others."
Gao had also attended a symposium run by the Beijing-based political magazine Yanhuang Chunqiu, according to former Xinhua journalist Yang Jisheng, now the magazine's deputy editor.
"Friends have told me that they have lost touch with Gao Yu, and I'm guessing that this won't be resolved until after the June 4 anniversary," Yang said.
"I think they want to silence her ahead of June 4."
He said Gao had recently spoken out in great detail about investigations into the family members and political allies of former security czar Zhou Yongkang, who is widely regarded as the next high-ranking target in President Xi Jinping's anti-corruption campaign.
"She spoke out a lot about that, and she was very active [on the topic]," Yang said, adding that Gao was likely to be found alongside her grown son, who is also incommunicado.
"She and her son will share the same fate," he said. "I think that the two of them are together right now, being prevented from speaking out."
In February, Gao launched a stinging attack on the former party secretary of the troubled northwestern region of Xinjiang, blaming Chinese policies there for a string of violent incidents in recent years.
She also hit out at the detention of outspoken ethnic Uyghur scholar Ilham Tohti.
"It has been the same in Tibet, and the same process has begun in Inner Mongolia. If the mistakes aren't corrected, this country will have no peace," she wrote in a Feb. 6 commentary aired on RFA's Mandarin Service.
"Punishing Ilham Tohti is the latest in a litany of errors."
Gao was first detained on June 3, 1989, as the People's Liberation Army (PLA) moved its tanks into the heart of Beijing, putting an end to weeks of occupation, mass protests and hunger strikes by students calling for democracy and the rule of law.
She was released after 450 days and jailed in November 1994 for "illegally providing state secrets to institutions outside China's borders," in connection with four articles she wrote in the Hong Kong-based Mirror Monthly magazine.
In 1997, she was presented with a U.S. $25,000 press freedom award in absentia by UNESCO Director General Fernando Mayor, sparking a furious reaction from Beijing.
There has so far been no official comment on her disappearance, CPJ's Dietz said.
Former top Communist Party aide Bao Tong, who has been held under house arrest at his Beijing home after serving a seven-year jail term in the wake of the 1989 crackdown, said Gao's disappearance marked a major threat to Chinese journalism.
"The disappearance of Gao Yu shows that the liberty and freedom of expression of Chinese people is under great threat," Bao wrote in a commentary on RFA's Mandarin Service on Monday.
"This well-known journalist had just celebrated her 70th birthday when the news of her disappearance came, spelling doom for Chinese journalism and for the civil rights movement," said Bao, a close friend of Gao's.
Reported by Qiao Long for RFA's Mandarin Service, and by Hai Nan for the Cantonese Service. Translated and written in English by Luisetta Mudie.