Sina apologised for "the suspected problem" of pornographic content on its literature and video sites. It said in a statement on its website that it felt "sorry and ashamed" for lax monitoring and that it had moved quickly to rectify the problem.
Citing a statement from the National Office Against Pornographic and Illegal Publications, the official Xinhua News Agency said authorities had found 20 articles and four videos containing pornographic and lewd content following public tip-offs. Some people are being investigated by police as a result, it said.
It said the state broadcasting authority had therefore decided to revoke Sina's licenses on Internet publishing and online audiovisual broadcasting and impose "a large number of fines."
China's communist authorities heavily police the Internet for content deemed obscene or politically subversive. Twitter, Facebook, and other western social media sites are blocked.
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In the government's latest campaign against online pornography, the State Internet Information Office had shut down 110 websites and some 3,300 accounts on China-based social networking sites as of the past weekend.
Mark Natkin, managing director of Marbridge Consulting, a Beijing-based internet and mobile research company, said he did not think the revoking of Sina's licenses would be permanent.
"Very frequently things of this nature are very campaign-based and as such temporary. There is some window given to the company to clean up," he said.