The Chinese government has extensive controls over paid-for internet ads and planned earlier to codify that policy in law.

For instance, last month Chinese regulators enforced limits on the number of profitable ads by Baido Inc, after a student who went through an experimental cancer treatment which he found using China’s biggest internet search engine.

Wei Zexi, 21, passed away in April due to a rare form of cancer, and the case sparked widespread public anger.

Today, China’s internet regulator said through a statement on Saturday that search engines should constrict management of paid-for ads in search results, to clarify which results are paid-for and limit their numbers.

The Cyberspace Administration of China said search engines should investigate the “aptitude” of clients offering paid-for ads, set a clear upper limit on such ads and clearly distinguish which are paid-for ads and which come from “natural searches”.

“Internet search providers should earnestly accept corporate responsibility toward society, and strengthen their own management in accordance with the law and rules, to provide objective, fair and authoritative search results to users,” it said.

Many internet users are worried because of medical ads which they consider as a threat to people’s health, according to the regulator.

“Baidu will work closely with government agencies, internet users and the community to uphold a healthy internet environment, and strive to provide objective, impartial, and authoritative search results to our users” said Baidu.

“Some search results contain rumors, obscenities, pornography, violence, murder, terrorism and other illegal information,” it said.

Officials say internet restrictions, including the blocking of popular foreign sites like Google and Facebook, are needed to ensure security in the face of rising threats, such as terrorism.

Foreign governments and business groups have pointed to restrictions on the internet as a broader trade issue.