China's cyber regulator has launched an investigation into countries largest social media platforms -Tencent's WeChat, Baidu's Tieba, and Sina's Weibo - for failing to manage prohibited content.

The Cyberspace Administration of China (CAC) issued a notice saying the three internet giants failed to comply with the Cybersecurity Law of the People's Republic of China, which allows authorities to prosecute anyone posting violent, obscene content, or something that the Communist Party deems offensive.

"Users are spreading violence, terror, false rumors, pornography and other hazards to national security, public safety, social order," the regulator said on its website. It added the platforms hosting such information have failed in their duty to manage sensitive content but didn't mention what exactly led to the probe.

While WeChat and Weibo, which collectively boast over 1 billion users, did not comment on the probe, Baidu has issued a statement saying the company is willing to comply with cybersecurity laws and will "actively cooperate with government departments to rectify the issue and increase the intensity of auditing". For now, there's no word on what actions may be taken the against the guilty platforms.

The investigation comes as China continues its crackdown against the country's top tech firms with a stringent stance towards censorship and an intent of taking down potential sources of disruptive information. Just last month, cyber security authorities flagged examples of illicit and prohibited content on the same platforms, prompting the same three firms to carry out an "immediate cleaning and rectification".

In June, CAC ordered the closing of over a dozen WeChat accounts that had been producing entertainment content, including music and movie commentaries. It said such sites should comply with the cybersecurity law and ensure the "correct direction of public opinion." Then, in the same month, Tieba forum - home to millions of discussions on a range of topics - asked its users to register with real names, citing the same law.