BEIJING - China's Internet regulator publicized a regulation Saturday on search engines, ordering search providers to ensure objective, fair and authoritative search results.

Search providers must improve censorship and remove any illegal content, according to the regulation released by the Cyberspace Administration of China.

All paid-for search results must be labeled clearly and checks on advertisers should be improved, according to the regulation. There should also be a limit on the number of paid-for results on a single page.

Moreover, the practice of blocking negative content concerning advertisers has been banned.

The regulation came after an investigation into Baidu, which was criticized for influencing the treatment choice of a late cancer patient, Wei Zexi, by presenting misguiding medical information.

Wei, 22, died after undergoing a controversial cancer treatment at a Beijing hospital, which the Wei family found through Baidu search.

"Search service providers should be aware of their social responsibility [...] they must provide objective, fair and authoritative search results to netizens," the CAC was quoted as saying later in a statement.

Paid listing were not distinguishable from normal search results, which could mislead users, the administration said. It has been reported that some medical organizations, which paid for search results, were unqualified or had forged certificates.

"The content of some search results was found to be rumors, pornographic, violent or related to terrorism," according to CAC.

Web directories must have a channel to receive complaints and compensate for any damages caused to users, but the regulation did not elaborate on this aspect.

Earlier this month, CAC asked Baidu to improve its paid-for listings model and to rank the search results mainly according to credibility rather than price-tags.