"People have the right to seek and receive information and to express their peaceful beliefs online without fear or interference," said Amnesty programme director Dan McQuillian.
"I call on governments to stop the unwarranted restriction of freedom of expression on the Internet, and on companies to stop helping them do it," he said.
Amnesty presented a petition with its call -- backed by 50,000 online signatures -- at a UN forum on Internet governance held at the southern Athens suburb of Vouliagmeni.
During the four-day forum, which brought together experts from over 90 states, IT firms, non-government organisations and users for the first time, corporations such as Microsoft, Cisco Systems, Google and Yahoo! were accused by human rights groups of helping the Chinese authorities suppress freedom of expression and monitor dissidents.
A recent case cited by Amnesty involves a Chinese journalist who was sentenced to 10 years in prison after emailing to a US-based website a Chinese internal government directive on how journalists should cover the anniversary of the Tiananmen Square crackdown.
The journalist was apprehended after the local email company Alibaba, a partner of global news engine Yahoo!, provided the authorities with his private information, Amnesty said.
"The Internet should be a force for political freedom, not repression," McQuillian said.
Cisco was accused at the UN forum by Reporters Without Borders of selling surveillance equipment to Chinese police.
Microsoft shut down the weblog of a Chinese New York times researcher on a request by Beijing, says Amnesty, while Google is accused of self-censoring its search engine to filter out terms deemed subversive by the Chinese authorities.
Countering the criticism, IT corporations said at the UN forum that their presence in China has given over 130 million local users access to the Internet and thereby access to more information.

Copyright AFP (Agence France-Presse), 2006