After 16 years, Tiananmen dissident Yu Dongyue was finally freed from prison yesterday, but with his mental health impaired. Amnesty International welcomed his release and called for all others still imprisoned in connection with the crackdown on the 1989 pro-democracy movement to be freed.

"This is an awful case," said Corinna-Barbara Francis, East Asia researcher at Amnesty International. "Yu Dongyue may at long last be out of prison, but 16 years of wrongful imprisonment with periodic beatings, torture and years in solitary confinement appear to have left him with his mental health severely damaged."

Yu Dongyue, journalist and deputy editor of the Liuyang Daily, was imprisoned in 1989 for 'counter-revolutionary sabotage and incitement' after throwing paint at the Tiananmen Square portrait of Mao Zedong. He was immediately put into solitary confinement for two years. Amnesty International considered him a prisoner of conscience.

According to a fellow dissident who visited him later in another prison he was subjected to beatings and torture. He showed scars on his head and other evidence of extensive abuse and appeared to have suffered a complete mental collapse -- he did not recognise life-long friends and kept repeating words over and over.

Other inmates said he had been tied to a pole and left in the sun for several days before being locked in solitary confinement for another two years. Upon his release, he reportedly could not recognise family members and kept mumbling to himself.

"At this time of Yu Dongyue's release we urge the Chinese authorities once again to launch an independent investigation into the brutal crackdown on the pro-democracy movement of June 1989," said Corinna-Barbara Francis. "The hundreds of victims have still not been given justice and the perpetrators must be charged and tried for their role in the killings and injuries."

There are still a number of other people locked up for their connection with the protests and others have been detained since then simply for campaigning for justice for the victims. "One might think the events of 1989 are long over but there are people still suffering in prison. The Chinese authorities must release them all immediately," said Corinna-Barbara Francis.

Among those still imprisoned in connection with the 1989 crackdown are Liu Zhihua, a worker at an electrical plant, and Hu Shigen, a lecturer at the Beijing Foreign Languages Institute. Liu Zhihua was arrested for taking part in a demonstration against the government's violent suppression of the pro-democracy movement just after 4 June 1989 with over 1,000 other workers at his factory in Hunan. He was sentenced to life imprisonment in 1989 for 'hooliganism' and 'injury with intent'. After sentence reductions, he is now due to be released in 2011.

Hu Shigen was a member of the 'Beijing 15', a group of labour and democracy activists. He was detained in 1992 for planning 4 June memorial activities and later tried for 'counter-revolutionary crimes'. As a senior member of the group, Hu received the heaviest sentence of 20 years in prison. His health has deteriorated so much that his friends fear he will not live to see his scheduled release in 2012. His family's requests for medical parole have not been answered by the authorities.