The Tibetan riots are undoubtedly not the kind of publicity China wants prior to the Olympics. In attempt to stem the flow of information, China has blocked access to some sites.
China has blocked access to Google News and YouTube in an apparent attempt to stop the spread of video footage related the rioting going on in several cities in Tibet, including the capital Lhasa. Demonstrations in the city started on March 10, a day commemorating the anniversary of a 1959 uprising against Chinese rule after which the spiritual leader of the country, the Dalai Lama, fled to India.
China has said the Dalai Lama is to blame for rioting in the country, and puts the civilian death toll at 13, while adding that police and security forces have also suffered casualties.
It appears China has borrowed tactics from Myanmar (AKA Burma) in this case. At the same time they haven't gone quite so far, as last September Myanmar blocked Internet access entirely for a time.