UN officials on Friday called on China to release of Chinese human rights lawyer Gao Zhisheng, who has been sent back to prison for three years.

"It is alarming that Mr Gao continues to be arbitrarily detained," said El Hadji Malick Sow, Chair-Rapporteur of the Working Group on Arbitrary Detention.

"His detention over the years has resulted in various human rights violations, including his fundamental right to a fair trial. I urge the authorities to release Mr Gao," Sow said.

"Under no circumstances should Mr Gao be subjected to attacks, including arbitrary detention", Frank La Rue, the Special Rapporteur on the promotion and protection of the right to freedom of opinion and expression, said.

The official Xinhua news agency said last Friday that Gao had been sent back to prison after a court ruled he had violated the terms of his probation.

Gao -- who defended some of China's most vulnerable people including Christians and coal miners -- was arrested in February 2009 and has been held incommunicado by the authorities.

He briefly reappeared in March last year when he was apparently released by police, speaking with a few friends and colleagues, many of whom reported that he continued to be tailed by authorities and was in ill-health.

A month later, he disappeared again and has not been heard from since.

Chinese activist jailed for nine years: lawyers
Beijing (AFP) Dec 23, 2011 - Veteran Chinese rights activist Chen Wei was sentenced Friday to nine years in jail for "subversion", his lawyers said, in one of the harshest penalties handed down in a crackdown launched this year.

Chen, who was a leader of the 1989 Tiananmen democracy protests, was among dozens of activists detained in February in the wake of political upheaval in the Arab world that sparked calls for anti-government demonstrations in China.

The court in Suining city in southwest Sichuan province convicted the 42-year-old after a trial lasting less than three hours over essays he had written that were critical of the Communist Party, China Human Rights Defenders said.

The sentence, for "inciting subversion of state power" was one of the toughest handed down so far to an activist detained in this year's crackdown, the group said.

After it was read out in court, Chen shouted out that he was innocent and declared "democracy will definitely prevail and dictators will definitely fall", his lawyer Liang Xiaojun told AFP.

Chen does not plan to appeal the sentence "because he feels this is a political sabotage and he does not want to perform any more pantomimes," Liang added.

Another lawyer, Zheng Jianwei, said the severe sentence was "terrifying" because it showed the government was willing to use trumped-up charges to silence critics.

"He is not guilty. He criticised the party and there was no law banning that," Zheng said.

"If everybody keeps quiet about politics and political reform then the country will not progress. It will be as harmonious as the party wants."

Chen has campaigned against human rights abuses in China for years.

He was imprisoned after the 1989 Tiananmen democracy protests and was a signatory to the Charter 08, a bold petition signed by thousands calling for political reform in one-party Communist-ruled China.

Activist group Amnesty International criticised the harshness of the sentence and called for Chen's immediate release.

"This extraordinarily long sentence is clearly retaliation for Chen Wei's peaceful advocacy of human rights and we are calling for his immediate and unconditional release," Catherine Baber, Amnesty's deputy Asia-Pacific director told AFP.

The charge of subversion is often used to put away government critics -- Nobel Peace Prize winner Liu Xiaobo was convicted on the same charge in 2009 and sentenced to 11 years in prison.

Another prominent democracy activist, Liu Xianbin, was imprisoned for 10 years in March amid the crackdown on dissidents over pro-democracy articles he had published online.

Joshua Rosenzweig, a human rights researcher at the Chinese University of Hong Kong, said Chen's lengthy sentence could be due to his previous convictions.

"The sentence has as much if not more to do with Chen's consistent political activism as it does with the ongoing crackdown," Rosenzweig told AFP.

The plight of human rights activists in China has come under the spotlight since Liu Xiaobo was awarded the prestigious Nobel prize in 2010, with the West pressing for the release of all political prisoners.

Chen's sentencing comes a week after prominent human rights lawyer Gao Zhisheng was sent back to prison just as his five-year suspended sentence was set to expire this week.