Amnesty International has called on the Chinese authorities to free all those who've been locked up for using the Internet to express their views or share information.
The group claims that at least 33 people - including writers and political activists - have been detained for Net-related offences.
Two of those died in custody apparently after being tortured by police. Both were members of the Falun Gong spiritual movement, which was banned as a "heretical organisation" in July 1999.
In another case a former police officer was sentenced for 11 years in prison after downloading articles from Chinese democracy Web sites. All his appeals have been turned down.
In its report People's Republic of China: State Control of the Internet in China, Amnesty International claims that in some extreme cases people could face a death sentence for publishing sensitive information on the Internet.
"Everyone detained purely for peacefully publishing their views or other information on the Internet or for accessing certain websites are prisoners of conscience," said Amnesty International in a statement.
"They should be released immediately and unconditionally".
China's unease with the very concept of the Internet has forced it to take strict measures to monitor people's usage of the Net.
For example, in the central Chinese province of Jiangxi people who use cybercafes now have their online activities monitored by police. Anyone who wants to use a cybercafe must now carry an Internet identity card containing personal details including their name and address. These details are then logged onto a police database.
And in the summer Chinese authorities were fingered for blocking access to Google.
Amnesty International's report can be found here.