Human rights group, PEN International announced late on Saturday that China had released prominent dissident and journalist Shi Tao from jail 15 months before the end of his sentence.
Shi had been jailed in 2005 for leaking state secrets abroad after Yahoo helped authorities identify him, PEN International said.
Shi was then sentenced to 10 years in prison. Yahoo defended itself at the time, saying it had to abide by local laws.
"We welcome news of Shi Tao's early release, at a time when there seem to be increasingly long shadows over freedom of expression in China," PEN International's Marian Botsford Fraser said in a statement.
"Shi Tao's arrest and imprisonment, because of the actions of Yahoo! China, signaled a decade ago the challenges to freedom of expression of Internet surveillance and privacy that we are now dealing with."
A Chinese rights activist in contact with Shi confirmed that he had been released just over a week ago. The activist, who asked not to be identified, said Shi was not accepting interviews for now.
It was not immediately clear why he had been let out early, though such releases can be granted in China due to good behavior in jail.
Shi's prosecution was based on an email he had sent to a New York-based website detailing media restrictions ahead of the 15th anniversary of the 1989 crackdown on pro-democracy protests in Tiananmen Square.
PEN said that Shi "was treated relatively well in prison during the last few years and wrote many poems, including 'Song of October' written from prison after he learned that Liu Xiaobo had been awarded the Nobel Peace Prize."
Liu was jailed in 2010 on subversion charges. New Chinese President Xi Jinping has shown no sign of wanting to release him or end the Communist Party's crackdown on dissidents and those challenging the party's authority.
China is in the midst of yet another push to rein in freedom of speech on the Internet. Authorities say it is a campaign to stop the spread of "irresponsible" rumors.
Yahoo shut its China email service last month as part of a gradual pull-back from the country since buying a stake in China's Alibaba Group Holding Ltd in 2005.