China censors social-media messages: Report

In the wake of a video documentary about air pollution in China gaining popularity earlier this year, hundreds of posts on Weibo, China's equivalent of Twitter, were also censored for commenting on the film and its findings, researchers have reported.

In March 2015, the video documentary entitled 'Under the Dome', went viral. The film was viewed more than 200 million times before it disappeared following government objection.

The film included the tale of a six-year-old girl, who says she has never seen white clouds, stars, or blue skies.

As links to the video went dead and commentary was pulled down, international journalists were quick to report on the story, but no one was aware of how many Weibo commenters had been suppressed.

"What they missed was that hundreds of posters were censored on 1 and 2 March, days before the video started disappearing from popular video-sharing sites", wrote the researchers.

Professor Matthew Auer from Bates College in Lewiston, US, and associate professor King-wa Fu, from University of Hong Kong reported their findings in the magazine Index on Censorship.

"Among the deleted messages we found condemnations of the state and photographs of anti-pollution demonstrations," they noted.

Some of the images taken down were of protesters with placards calling for the government to reduce the "haze" (air pollution):

"By the standards of Chinese censors, the messages conveyed by the protesters were not the problem. It is that they are demonstrating in the first place"" the report said.

"The panicky removal of the video from Chinese websites, followed by censorship of not only official commentary, but also the views of ordinary citizens, suggests that the state remains more effective at clamping down on public expression than on pollution," the report noted.

The full report includes examples of censored Weibo posts and an explanation of how they were tracked. The University of Hong Kong's Weiboscope project monitors 350,000 popular Weibo accounts.