Works by purged Chinese leader Zhao published in Hong Kong

A trove of newly published documents belonging to a purged Chinese leader has been launched at Hong Kong's book fair, despite fears Beijing is tightening freedom of expression in the city.

Former premier and Communist Party general secretary Zhao Ziyang was removed from China's top political leadership after he showed sympathy for students ahead of the bloody crackdown on their pro-democracy movement in Tiananmen Square in 1989.

He then spent 16 years under house arrest before his death in 2005.

Book (bottom, C) containing a collection of documents by late Chinese Party chief Zhao Ziyang, newly published by the Chinese University of Hong Kong Press, along with a photo of him, displayed at the Hong Kong Book Fair on July 20, 2016 ©Anthony Wallace (AFP)

The new book could anger Beijing and will strike a chord in Hong Kong, where some publishers have been scared off bringing out controversial titles after the disappearance of five booksellers from the city -- they later resurfaced in the mainland where one is still detained.

All worked for a company known for gossipy titles on Chinese leaders.

The material for the new book was brought out of China by Zhao's former aides, according to a publishing official who did not want to be named.

She said it would be "self-censorship" not to publish due to fears it could anger Beijing.

"These are not libellous writings...It is based on facts," she said.

The "Collected Works of Zhao Ziyang", published by Hong Kong's Chinese University Press, is a four-volume compilation of previously unseen policy documents, speeches and letters mainly by Zhao from 1980 to 1989, shortly before his fall.

While they do not mention the 1989 protests, they lay out his liberal views -- including pushing for democratic reform within the Communist Party and calling for less censorship of artistic works.

In one letter he reassures Hong Kong students during 1984 negotiations with its then colonial ruler Britain for the handover of the city back to China.

"You all can completely trust that the Chinese government will definitely take policies and measures, when resolving the issue over Hong Kong, in the wishes and interests of Hong Kong compatriots," he says.

Zhao is revered by Chinese human rights defenders, in part for opposing the use of force to quell the Tiananmen Square democracy protests, when hundreds of unarmed civilians -- by some estimates, more than 1,000 -- were killed.

The new book is for sale at the Chinese University Press booth at the annual book fair, with a constant flow of customers to the stall.

The fair has always been a source of books that would be banned on the mainland, with many readers crossing the border to browse titles banned at home.

Several publishers at this year's fair are still offering books likely to rile Beijing, despite the bookseller saga.

"This is a monumental effort in publishing," said Hong Kong-based publisher Bao Pu of the new book.

"Despite the pressure there are still efforts to do the right thing in the publishing industry," added Bao, who separately brought out Zhao's memoirs in 2009.

Zhao Ziyang, China's then prime minister, Communist Party (CCP) general secretary, pictured during the 13th Communist Party Congress at the People's Great Hall in Beijing on November 1, 1987 ©John Giannini (AFP/File)

Bao Tong, a former Chinese government official jailed for opposing the 1989 Tiananmen Square crackdown, holds up a photo of his former boss Zhao Ziyang during an interview at his home in Beijing on February 22, 2011 ©Goh Chai Hin (AFP/File)