Chinese authorities have ordered a major social media platform to curb "harmful content" more effectively as they intensify oversight of online expression -- even taking aim at rap music, crude cartoons, dirty jokes and celebrity gossip.

The campaign is intended not just to stamp out dissent but to ensure that all media "serves the direction of socialism".

Sina Weibo has failed to comply, Beijing's Cyberspace Administration said Saturday on its official WeChat social media account, berating the site for letting users post "content of wrong public opinion orientation, obscenity, low taste and ethnic discrimination".

The company "has violated the country's laws and regulations, led online public opinions to wrong direction and left a very bad influence," it said.

China has some of the world's tightest controls over web content, protected by what is called "The Great Firewall". Restrictions on free speech have increased since President Xi Jinping assumed power in 2012.

A controversial cybersecurity law, which took effect last June, has given authorities even more leeway to regulate a wide variety of information.