Yu Dongyue threw paint at this portrait of Mao

Yu Dongyue was sentenced to 20 years in jail for throwing paint at a portrait of China's former leader Mao Zedong.

He was freed on Wednesday, after 17 years in prison, but family members said he did not recognise them and spoke unintelligibly.

Human rights groups have alleged Yu was tortured by guards in prison.

His father, Yu Yingkui, said the family would now try to find ways to treat his mental problems.

1989 TIANANMEN EVENTS 15 April: Reformist leader Hu Yaobang dies 22 April: Hu's memorial service. Thousands call for faster reforms 13 May: Students begin hunger strike as power struggle grips Communist Party 15 May: Soviet leader Mikhail Gorbachev visits China 19 May: Zhao makes tearful appeal to students in Tiananmen Square to leave 20 May: Martial law declared in Beijing 3-4 June: Security forces clear the square, killing hundreds

"He is suffering from mental illness... he gives few responses and has not said anything," he told the AFP news agency.

'Solitary confinement'

Yu, a journalist and critic for a Hunan newspaper, was one of three men arrested for throwing paint at the Mao portrait in May 1989, at the height of the Tiananmen Square pro-democracy protests.

The three were later jailed for "counter-revolutionary destruction and counter-revolutionary incitement".

One of the three, Lu Decheng, was released in 1998, and later visited Yu in prison.

Lu told Radio Free Asia in 2004 that his friend was "barely recognisable".

"He had a big scar on the right side of his head. A fellow prisoner said Yu had been tied to a electricity pole and left out in the hot sun for several days. He was also kept in solitary confinement for two years and that was what broke him," Lu said.

Chinese police and troops killed hundreds of unarmed demonstrators when they broke up the Tiananmen Square protests on 4 June 1989.

John Kamm, a US campaigner who had called for Yu's release, said he knew of 70 other prisoners jailed for the Tiananmen protests, although many were convicted on criminal damage rather than political charges.

China outlawed torture in 1996. But a UN rapporteur who visited China last year, Manfred Nowak, said it remained widely in use across the country.

Torture methods cited in a statement at the end of his visit included use of electric shock batons, cigarette burns, and submersion in pits of water or sewage.