Douban administrators told the user that posting pornography online would endanger the site's operations.

In response, the organisers of the protest asked Internet users to clothe images in artworks to "save" them from censors, who have shut down 1,635 websites and 200 blogs in a one-month campaign against content that "harms public morality".

Over four million porn-related posts or messages have been deleted and China has vowed to extend the anti-porn push to content uploaded to cellphone websites, chatrooms and instant-messenger groups, reported Xinhua.

The nude-reclothing protest is not limited to 16th-century art. One netizen drew red underpants on an image of the leaning, joined towers of state-run China Central Television's headquarters in Beijing.

However, protest organisers were cautious about overstepping the boundary. Participants were urged not to depict China's political leaders in their images.

"Netizens in China are becoming more and more innovative in their ways of protesting against the censorship authorities' arbitrary use of power," blogger Catherine Yeung wrote in a comment on the protest campaign.

The protest had an almost immediate effect.

Last Thursday, the Shanghai user whose Renaissance album started the controversy said Douban had allowed images of the deleted paintings to be shown in their original form.