Image caption Lawyer Gao Zhisheng has defended human rights activists and minority groups in China.

One of China's best known dissidents, missing for 20 months, is now said to be in a Xinjiang prison.

Gao Zhisheng, a lawyer, was arrested in February 2009, released briefly in March 2010 and disappeared soon after.

The official Xinhua news agency reported last month that Mr Gao had been sent back to jail for three years for violating probation rules.

On Sunday his brother said he had received a court document saying his brother was in jail in Xinjiang.

Gao Zhiyi said he planned to visit his brother in the Shaya County jail in the western prefecture of Aksu later this month.

"I did not know where my brother was for over a year,'' he told AFP news agency. ''I always knew that he was not free and he was under control of the government and state security."

In the 1950s and 60s, political prisoners were often sent to Xinjiang.

Human rights activists, responding to the news, said that imprisoning Mr Gao in the remote area was an attempt to deter visitors.

'Subversion' charges

Gao Zhisheng timeline: 2005: Authorities close down Gao Zhisheng's law practice

Dec 2006: Convicted of subversion and sentenced to house arrest

Sept 2007: Says he was tortured during a period of detention

Jan 2009: Disappears; last seen accompanied by security officials

Mar 2010: Reappeared for a month before disappearing again

Dec 2011: State media says he has been jailed for three years

Gao Zhisheng, a 45-year-old attorney who has defended activists and religious minorities, is an outspoken critic of the Chinese government.

He was detained by authorities before his disappearance and also said he had been tortured.

Human rights advocates often cite his case along with that of Liu Xiaobo, the jailed academic awarded the 2010 Nobel Peace Prize, as examples of what they say is the Chinese Communist Party's increasing persecution of human rights defenders in China.

Mr Gao was sentenced on charges of "inciting subversion of state power", his brother told Reuters over the phone from Shaanxi province.

Mr Gao's wife, Geng He, and two children sought asylum in the United States in early 2009.

The US, European Union and United Nations have repeatedly called on Chinese authorities to release him.