The decision to award jailed Chinese dissident Liu Xiaobo the Nobel Peace Prize a year ago provoked a furious reaction from Beijing, which has since placed a shroud of silence around him and his family.

Convicted for subversion in December 2009 for co-writing the pro-democracy manifesto Charter 08, Liu became the first Chinese citizen ever to win the prestigious Nobel peace award on October 8 last year.

In the 12 months since then, rights groups say the government has placed Liu's wife under house arrest without charge and violated Chinese law by not allowing him monthly family visits.

This week, as the first anniversary of the award loomed, it emerged that authorities had in recent months permitted visits by Liu's brothers and his wife Liu Xia, and allowed him to leave jail briefly after his father's death.

Liu Xiaoxuan, one of the 55-year-old dissident's brothers, said Liu Xia had finally been allowed to visit her husband in August at the prison in northeast China's Liaoning province where he is serving his 11-year sentence.

Only a week earlier, Liu Xiaoxuan had told AFP he was unable to conduct interviews concerning the circumstances surrounding his brother.

Wang Songlian, a researcher at the Hong Kong-based Chinese Human Rights Defenders, said the timing of his announcement was likely significant.

The brother "didn't release any details on (Liu Xiaobo's) condition... (which) is still worrying," said Wang.

"This is probably one of the calculated moves by the Chinese government to release information through the channel of the brothers, because they know people would ask questions... ahead of the anniversary," she added.

Jean-Philippe Beja, an expert on China at the Paris-based CERI-Sciences-Po, said the recent visits were "simply to show... that his prison conditions are not atrocious and (to show) a bit of humanity before the awarding of the new Nobel Peace Prize".

But "a little humanity does not change the fact they continue to operate illegally," Beja, who has been close to Liu, said of Liu Xia's house arrest and the failure to grant monthly prison visits.

Activists also said the decision to allow Liu to leave prison briefly did not signal any prospects of an early release for the dissident, who was little known either in China or abroad before he won the Nobel.

"There are no signs whatsoever pointing to an early release of Liu Xiaobo," Nicholas Bequelin of Human Rights Watch told AFP.

It "will depend mostly on how much international pressure there is on his case... and how concerned China will be about being the only country in the world holding a Nobel Peace Prize laureate in prison."

Liu's prospects may improve following the retirement of China's top leaders slated at a Communist Party congress next year, but will also depend on increased global pressure, he said.

Despite few signs of an imminent release, some at least hope that Liu will not have to serve the whole of his sentence.

Liu's lawyer Shang Baojun said that according to Chinese law Liu could theoretically be released after completing half of his sentence. The imprisonment of a Nobel laureate was "not good for China", he added.

But democracy activist He Depu, released from eight years in prison in February as a member of the outlawed China Democracy Party, said Liu's chances of being freed were diminished because he "has refused to admit his guilt".

"It is difficult to see any measure of leniency until (next year's Communist Party) congress, but one never knows because of the political infighting at the top," Beja said, referring to the top-level five-yearly meeting.

Liu, who suffers from hepatitis, could also be released on medical grounds, as were several dissidents linked to the 1989 Tiananmen democracy protests, he said.

Overseas calls for China to release Liu -- who in a powerful and provocative gesture was represented by an empty chair at the Nobel award ceremony in Oslo in December -- are now made discreetly.

Wang from Chinese Human Rights Defenders said the absence of any information from Liu or his family made it difficult to keep up the pressure.