An international journalism advocacy group says the U.S.-based Yahoo Internet company works regularly with Chinese police to supply information on dissidents who use its service.
In a statement issued Thursday, the Paris-based organization Reporters Without Borders called on Yahoo to release a list of all the dissidents on whom it has provided data.
The group says it has discovered that Yahoo provided information relating to the arrest of at least two jailed dissidents, one in 2003 and the other last year. Reporters Without Borders says the men received sentences of eight and 10 years, both based on electronic data supplied by Yahoo.
Yahoo spokeswoman Mary Osako says that when the company receives subpoenas it is not usually told how the information is being used.
A U.S. congressional committee will hold a hearing next week on ethical responsibilities of Internet companies.
Some information for this report was provided by AP and Reuters.