The website of the state-run 21st Century Business Herald newspaper and the weekly publication Money Week were penalised after they were found to have forced clients to sign advertisement and service contracts by threatening to publish negative news about them, the State Administration of Press, Publication, Radio, Film and Television (SAPPRFT) said in a statement.
The website and weekly - affiliated with 21st Century Media Ltd - along with the Herald newspaper were also found to have irregular management practices, It said.
About 30 suspects involved in the cases, including Shen Hao, former president of 21st Century Media Ltd, were arrested and put under criminal investigation for forced transactions, blackmail, breach of duty and accepting bribes.
In February, prosecutors started to review their cases and prepare for prosecution, state-run Xinhua news agency reported.
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"Media involved in blackmail have had a vile social impact, seriously harmed public interests, undermined market order and marred the credibility and image of journalists," SAPPRFT said.
It warned all media organisations to learn from the incident and step up their internal regulation of news reporting.
Almost all media in China is state owned or state controlled.