A Chinese court said Monday it had jailed veteran activist Chen Xi for 10 years for subversion, one of the longest sentences yet to be handed down in this year's crackdown on dissent.

The court in the southwestern province of Guizhou convicted Chen, who was involved in the 1989 Tiananmen democracy protest movement, after a trial lasting just a few hours, Chinese Human Rights Defenders (CHRD) said.

An official at the court confirmed Chen had been sentenced to 10 years for "subversion of state power", a ruling that comes days after another Chinese dissident was jailed for nine years.

Activists believe the charge was related to essays the 57-year-old had written on advancing political reform and improving human rights in China.

Authorities launched a crackdown on criticism of the one-party government this year following anonymous Internet calls for protests in China sparked by the political upheaval in the Arab world.

Scores of activists and rights lawyers were rounded up after the emergence of the "Jasmine" campaign, which went largely unheeded, sparking US accusations of China's "serious backsliding" on human rights.

On Friday, fellow veteran democracy activist Chen Wei, who is not believed to be related to Chen Xi, was sentenced to nine years for subversion in the southwestern province of Sichuan.

"In both cases, sentences were handed down with minimal court deliberation, strongly suggesting that the verdicts had been determined before the trial even began," Joshua Rosenzweig, an expert on China's human rights at the Chinese University of Hong Kong, told AFP.

"This is very troubling, yet more evidence of the authorities' willingness to take advantage of vague statutes nominally aimed at protecting national security to silence those like Chen Xi and Chen Wei who persist in pressing for political change."

Chen Wei, who was a leader of the Tiananmen democracy protests, was sentenced after a trial lasting less than three hours over essays he had written that were critical of the Communist Party.

UN human rights chief Navi Pillay Monday said the "extremely harsh sentencing" of Chen Wei indicates a "further tightening of the severe restrictions on the scope of freedom of expression in China".

Chen Xi's family was informed of the trial on Saturday and told that three family members would be allowed to attend, CHRD said.

The activist, who is a leading member of the Guizhou Human Rights Research and Discussion Association, was taken into police custody on November 29, when police ransacked his home, confiscating his computer, the rights group said.

He served three years in prison for his role in the 1989 protests and was sentenced again to 10 years in prison for subversion in 1995 for advocating democracy, the Hong Kong-based Information Centre for Human Rights said.

Along with Chen Wei, Chen Xi was a signatory to the Charter 08, a bold petition signed by thousands calling for political reform in one-party Communist-ruled China.

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.

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

The sentencing of Chen Xi and Chen Wei comes after prominent human rights lawyer Gao Zhisheng was sent back to prison just as his five-year suspended sentence was set to expire last week.