China has defended the use of new screening software that has to be installed on all computers.
A foreign ministry spokesman says the software will filter out pornographic or violent material but critics have complained that it could also be used to stop Chinese internet users searching for politically sensitive information.
All computers sold in China, including those that are imported, will have to be pre-installed with the software.
Microsoft says the plan raises the issues of freedom of expression, privacy and security.
--- BBC says