China has shut down more than 100 websites carrying pornography and closed thousands of accounts on social media sites in an renewed effort to clean up the Internet, state media reported.

The campaign, named Cleaning the Web 2014, was launched in response to the spread of online pornography despite repeated bans, according to a circular issued by the National Office Against Pornographic and Illegal Publications.

Pornography is illegal in China, but some overseas critics are concerned that the crackdown on material deemed obscene is the latest government attempt to tighten its grip on the internet and will be used in broader censorship of websites.