A leading Chinese dissident lawyer and his relatives have been "threatened" since his daughter spoke about his controversial new book in Hong Kong this week, the daughter and activists said Friday.

Gao Zhisheng's current whereabouts are unknown after Chinese security agents are said to have rushed to his brother's house, where he is staying, in an isolated village in China's Shaanxi province on Tuesday.

Gao has been under house arrest since 2014 after serving a three-year prison term on subversion-related charges -- a sentence which sparked an international outcry.

"I am worried they will face many threats... I already know that right after (his daughter) Grace's press conference in Hong Kong, Chinese security personnel rushed to his brother's house and threatened (them)," said Bob Fu, president of US-based human rights group China Aid Association which co-published the book.

"We don't know if he has been removed from his cave home in Shaanxi. We don't know where he is now," Fu said, adding that a local contact who passed on the information of the security agents' visit had also gone "missing".

Speaking in Taipei to launch her father's new book "Stand Up China 2017" -- which predicts the demise of the Communist Party and details his torture at the hands of the authorities -- Grace Gao said her uncle and aunt's mobile phones were disconnected or turned off when she called them on Friday.

She felt her father would be subject to punishment over the book but added: "He is prepared for anything and our family is prepared."

Gao fell foul of Chinese authorities by championing the rights of vulnerable people including underground Christians, aggrieved miners and members of the banned Falungong spiritual movement.

He was convicted in 2006 of "subversion of state power" and given a three-year suspended prison sentence. State media said in 2011 that he had been ordered to serve the sentence after a Beijing court ruled he had violated the terms of his probation.

In the 446-page book, Gao predicted the demise of the Chinese Communist Party in 2017, saying that "peaceful power for change" will flourish in China despite brutal suppression and it is "enviable for China's evil forces to demise".

Gao detailed what he called abductions and tortures imposed on him by Chinese authorities since 2004, including electric shocks.

The book was published by two human rights groups as no publisher in Taiwan or Hong Kong wanted to get involved, according to co-publisher Taiwan Association for China Human Rights.

"Please help my family and all Chinese people," Grace Gao wrote in a copy of the book to be given to Taiwan's President Tsai Ing-wen through a lawmaker of Tsai's party.

"I hope she will do her best or within her power to help with human rights in China," she said.

Hong Kong people 'petrified' over bookseller revelations
Hong Kong (AFP) June 17, 2016 - Hong Kong lawmakers say residents have been left "petrified" by explosive revelations from a city bookseller about his detention in China and have slammed Beijing for violating freedoms.

In a surprise interview Lam Wing-kee broke his silence Thursday over how he had been detained on a visit to China and was interrogated for months with no access to a lawyer or his family. He vowed to break bail, refusing to return to the mainland.

Lam, 61, is one of five booksellers who published salacious titles about leading Chinese politicians and disappeared at the end of last year in a case that drew international condemnation and heightened fears Beijing was tightening its grip on semi-autonomous Hong Kong.

Pro-democracy lawmakers accused Hong Kong authorities of failing to help the booksellers and called on them to ensure Lam is now kept safe after his decision to speak out.

Emily Lau of the Democratic Party said if Lam were harmed it would "shatter" Hong Kong.

"Many Hong Kong people are petrified," she told AFP.

"It can happen to each and every one of us."

The government says it is trying to speak to Lam and that residents' safety is paramount.

China's foreign ministry would not be drawn on the criticisms of its treatment of Lam, saying only that he had violated Chinese law.

"Authorities here have the right to deal with the relevant case in accordance with the law," said spokeswoman Hua Chunying Friday.

One pro-democracy lawmaker said Chinese authorities were acting like "thugs" and accused the Hong Kong government of being a puppet of Beijing.

"Hong Kong is being pathetic," said Claudia Mo of the Civic Party.

"It has to say something to regain people's confidence... but it is terrified to do anything that might embarrass Beijing."

Some residents said they now questioned how safe they are in Hong Kong.

"People feel scared," accountant Louis Chan, 28, told AFP.

"Now the Chinese government want to have full control."

- Protesters gather -

A succession of political groups protested outside China's liaison office in Hong Kong Friday with more demonstrations expected Saturday.

High-profile teenage activist Joshua Wong called Lam a hero.

"Lam is the role model for Hong Kong people -- facing the suppression of the communist regime," Wong said.

Lam was kept in detention for eight months and returned to Hong Kong Tuesday. He was due to go back over the border Thursday but decided to speak out instead.

Lam told how he recited a scripted confession about involvement in the illegal book trade on state television in fear of what would happen to him.

In harrowing detail he also explained how the toothbrush he was given in detention was tied by a thread which was held by a guard to prevent him from committing suicide by swallowing it.

Fellow booksellers Lui Por and Cheung Chi-ping returned to Hong Kong in March on bail, but both were reported to have quickly gone back to the mainland.

Their colleague Lee Bo, who says he went to China of his own free will and is helping mainland authorities with their inquiries, has also been back and forth to Hong Kong.

Lee's case caused the most outcry because he was the only bookseller who disappeared on Hong Kong soil, prompting allegations that Chinese enforcement agents were operating illegally in the city.

The fifth man, Swedish citizen Gui Minhai, remains in detention.

The Swedish embassy in Beijing said Friday that repeated requests for a meeting with Gui had not been granted since they last saw him in February.