An international press freedom group has accused some of the world's leading technology firms of aiding the Chinese Government in censoring the internet.
Reporters Without Borders said some of the companies supplied China with sophisticated spying products.
Others simple turn a blind eye to Beijing's actions, the group says.
It says 46 people are in prison in China for setting up independent news websites or criticising the government on the internet.
In a letter sent to the heads of 14 companies, it said they should feel responsible for the plight of what it called China's embattled internet users.
Foreign media have described them as cyber-dissidents.
Last week, China released one woman, Liu Di, after detaining her for more than a year for her internet activities.
From the newsroom of the BBC World Service