BEIJING (AFP) - Liu Xiaobo, who was awarded the 2010 Nobel Peace Prize on Friday, has been a vocal champion for greater democracy and human rights protection in China for decades.

The 54-year-old, who was previously jailed for his involvement in the 1989 Tiananmen pro-democracy protests, was sentenced in December to 11 more years in prison for subversion -- a punishment that earned international condemnation.

Liu was arrested in late 2008 after co-writing Charter 08, a widely circulated petition that called for political reform in the Communist-ruled nation.

The bold manifesto, which has been signed by more than 10,000 people since it went online, calls for the protection of basic human rights and the reform of China's one-party system.

"The government opposes (giving the Nobel Peace Prize to him) because they fear that it will draw more attention to Liu Xiaobo and to China's situation (on democracy and human rights)," his wife Liu Xia told AFP earlier this week.

"If they didn't fear this, then they would not have sentenced him to 11 years for writing an essay."

Charter 08 specifically demands the abolition of subversion in China's criminal code -- the very crime for which Liu has been jailed.

"We should make freedom of speech, freedom of the press and academic freedom universal, thereby guaranteeing that citizens can be informed and can exercise their right of political supervision," the manifesto says.

"We should end the practice of viewing words as crimes."

Liu is also known for his efforts to help negotiate the safe exit from Tiananmen Square of thousands of student demonstrators on the night of June 3, 1989 when the military quelled six weeks of protests in the heart of Beijing.

He was arrested immediately after the crackdown and released without charge in early 1991.

Liu was re-arrested and served three years in a labour camp from 1996-1999 for seeking the release of those jailed in the Tiananmen protests and for opposing the government's verdict that they amounted to a counter-revolutionary rebellion.

The holder of a doctorate in Chinese literature, Liu was once a professor at Beijing Normal University, but was banned from teaching at state institutions over his involvement in the 1989 demonstrations.

As a leading member of the Independent China Pen Centre, a grouping of Chinese writers, Liu had remained in close contact with key intellectuals and had been largely free to attend meetings and writer group activities despite constant police surveillance.

Although Liu has been banned from publishing in China, many of his writings advocating greater democracy and respect for human rights have appeared in Hong Kong and overseas Chinese publications.

Some of these writings, which can be downloaded from the Internet inside China, served as evidence in his most recent trial, rights groups said.

Liu continues to command great respect from ordinary Chinese intellectuals, a fact that some say was central to the Communist Party's decision to bring charges against him.

Since his arrest, Western governments, rights groups, scholars, and a coalition of Nobel Prize winners have called for his release. The United States and the European Union earlier this year also demanded his immediate release.

Liu has been honoured by Human Rights Watch, Reporters Without Borders and other rights groups. His essay "The Noble Paradise of Power, the Hell for the Meek" won the Hong Kong Human Rights News Prize in 2004.

Liu is married, but has no children. His wife has remained under police surveillance at the couple's home in central Beijing since her husband was imprisoned.