An official with the General Administration of Press and Publication said websites which failed to remove the content would be taken offline.
The crackdown comes as China continues to tighten control over its booming Internet sector.
Since the second half of last year, it has introduced new regulations on online pornography.
Late last year, China cracked down on mobile websites offering pornography downloads and more recently it barred online game companies from using lewd marketing tactics to attract users.
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