China, hardly known for its press freedoms, announced this week that journalists there can no longer use “unauthorized” news sources.

In its announcement (which you can see here in Mandarin), the General Administration of Press, Publication, Radio, Film and Television, China’s media overseer, announced: "All kinds of media work units may not use any unauthorized news products provided by foreign media or foreign websites.”

The edict, which published the announcement in its own newspapers (China Press and Publishing Journal) was also extended to "informers, freelancers, NGOs, commercial organizations" that have not received government permission to be cited.

David Bandurski, the editor of Hong Kong University’s China Media Project, told London Telegraph correspondent Tom Phillips that the measure is part of the government's recent efforts to “control press content at its source.”

The new ruling also demands that Chinese media companies “strengthen management” of the content on their websites, blogs and micro-blogs, including private accounts of their employees. Sina Weibo is China’s version of Twitter that has become an immensely popular venue for the exchange of information among Chinese citizens.

The gag order effectively makes it illegal for Chinese media to aggregate user-provided content from Weibo, such as commentary over the Boston Marathon bombing or, more importantly, online chatter about this week’s announcement that The New York Times won the Pulitzer Prize for coverage of former Communist Premier Wen Jiabao’s extensive family wealth. The story led Chinese officials to block access to the Times website. In January, a provincial censor ordered Southern Weekly, a newspaper based in the southern city of Guangzhou , to remove an editorial calling for political reform and replace it with a column praising the Communist Party. The move led to a rare political protest calling for greater press freedoms, as reported in The Guardian.