BEIJING (REUTERS) - Executives of a respected business newspaper website confessed on state television that they extorted companies that planned to list for "huge payments" in exchange for quashing critical stories.

The official Xinhua news agency reported last month that eight suspects, including those working at the 21st Century Business Herald and at two public relations firms, were under investigation.

Liu Dong, president of the paper's website, and Zhou Bin, the website's editor in chief, had colluded with other colleagues and two financial public relations firms to solicit protection money from firms that were about to list or be restructured, Xinhua said on Thursday.

The two appeared on state broadcaster China Central Television wearing bright orange garb confessing to the crimes.

Chinese media often convicts people of crimes before they have even been charged, let alone appeared in court, jeopardising the prospects of a fair trial.

Liu and Zhou were taken into custody last week along with an advertising manager and a reporter. Two executives at financial public relations firms Roya Investment Services Limited, based in Shanghai, and Nukirin Investment Advisory, in the southern city of Shenzhen, were also detained.

The group extorted money from more than 100 companies since November 2013, Xinhhua reported. They demanded "huge payments"for positive coverage, as well as "protection money" to kill negative reports.

It is unclear whether any of the suspects has retained a lawyer. The 21st Century Business Herald could not be reached for comment.

The website would charge companies between 200,000 (S$32,600) and 300,000 yuan ($48,930) in the form of advertising contracts to delete critical articles.

State media has been the key vehicle for party propaganda, but reforms over the past decade have allowed greater commercialisation and some increase in editorial independence.

The news comes amid a crackdown at CCTV, where prosecutors have detained a top news anchor and a senior executive is being investigated on suspicion of bribery.

China media watchers have said blackmail is a widespread practice in the domestic press and journalists are susceptible to bribes.

Last year, the 21st Century Business Herald published a series of stories alleging bribery among foreign and local pharmaceutical companies, citing unidentified whistleblowers.