A leading Chinese dissident, Wang Youcai, has been released from jail and is headed to the US.
Wang Youcai will seek medical treatment in the US
Mr Wang, one of the founders of the outlawed China Democracy Party, was sentenced to 11 years in jail in 1998.
He has left for San Francisco, where he will receive medical treatment, John Kamm of the Dui Hua Foundation said.
His release comes ahead of an annual UN human rights meeting in Geneva at which the US was considering criticising China's rights record.
He left the Zhejiang No 1 prison in Hangzhou, southern China, early on Thursday.
The US government has welcomed Mr Wang's release, with State Department spokesman Richard Boucher saying that he had been "imprisoned for attempting to exercise basic freedoms of speech and assembly and China".
"We once again call on Chinese government to release all prisoners detained for peaceful expression of their views," Mr Boucher added.
"Clearly, I think, they (the Chinese authorities) have been releasing and giving sentence reductions to people who are considered priority cases by the United States," Mr Kamm told The Associated Press.
CHINA DEMOCRACY PARTY
Set up by dissidents in 1998
First attempt to legally register an opposition party
Quickly crushed by Communist Party
At least 30 members sentenced to jail terms of up to 13 years
Co-founders Xu Wenli released 2002, Qin Yongmin still imprisoned
"It's part of an overall effort to get the human rights dialogue back on track," he said.
Mr Wang, 37, first came to prominence as one of the student leaders involved in the 1989 Tiananmen Square demonstrations, which were brutally suppressed by the Chinese authorities at the cost of several hundred lives.
Mr Wang, a physics graduate from Peking University, was described by the authorities as one of the "most wanted" students, and was jailed for taking part in the protests.
In 1998 he was sentenced again, for his part in founding the China Democracy Party, the first attempt to set up a legal opposition to China's ruling Communist Party.
Communist officials outlawed the party soon after its inception, jailing more than 30 people for taking part.
Mr Wang was tried on the charge of "subverting state power", and was accused of organising meetings, using computer e-mail to send information and accepting donations from overseas.
His release, more than five years ahead of schedule, comes on the eve of the Chinese parliament's National People's Congress, which is expected to enshrine a commitment to human rights in China's constitution.
The Dui Hua Foundation said Mr Wang had suffered from bronchial disorders and
was recently diagnosed with myocarditis, an inflammation or degeneration of the heart's muscle tissue.
But it is difficult to determine how far his medical conditions played a part in his release.
A BBC correspondent in Beijing, Louisa Lim, says that medical parole for treatment overseas is often used as a way to send unwanted individuals into exile.
The release came one day after Chinese authorities cut the sentence of another prominent prisoner - the Uighur businesswoman Rabiya Kadeer.
She was sentenced to eight years in jail in 2000 on charges of separatism, but is now due to be released in August 2006, or even sooner, according to the Dui Hua Foundation.