Police in Shanghai are investigating eight people, including senior editors of news website 21cbh.com, on suspicion of extortion.

Experts have pointed to corruption within the ranks of Chinese media, arguing that blackmail is widespread and journalists are susceptible to bribery.

China has cracked down on official corruption and extravagance since President Xi Jinping took office last year.

Police have taken "coercive measures against the eight suspects" in line with the law, Xinhuanet quoted the Shanghai Public Security Bureau as saying.

The eight suspects include senior editors of the news website and people working at two public relations firms, Xinhua said. It did not give their full names.

The website is based on the content of the 21st Century Business Herald that is widely considered an influential business daily.

Both the website and the newspaper are run by Guangzhou-based Nanfang Media Group.

The 21st Century Business Herald said in a statement on Thursday that several employees of its website were taken away by the public security department for investigation at the night of Wednesday.

"The 21cbh.com will cooperate with police in the investigation. Before the final result comes out, the website will provide service to public professionally and objectively, and handle related issues in a responsible way," the statement read.

Xinhua said the editor in chief of the paper's website, whose surname is Liu; its deputy editor, surnamed Zhou; and other members of the editorial and operations staffs had colluded with two financial public relations firms in Shanghai and the southern city of Shenzhen to target firms that were about to be listed or restructured to "carry out illegal activities".

Citing the police investigation that started last year, Xinhua said: "After accepting high fees from the businesses that were willing to engage in 'positive propaganda' , the suspects would exaggerate positive facts or conceal negative issues."

If companies did not cooperate, the newspaper would "release negative reports maliciously attacking them" and "blackmail" them into signing advertising or cooperation deals, Xinhua said.

Although all Chinese media are controlled by State-run institutions, many news outfits such as the 21st Century Business Herald are subject to commercial pressures.

The news comes a month after prosecutors investigated Rui Chenggang, a top Chinese news anchor at China Central Television. In June, China's top prosecutor said it was investigating a senior executive with CCTV on suspicion of bribery. Rui was considered a star journalist in China, but he was also one of the investors in the public relations firm Pegasus. The Chinese company was acquired by the American agency Edelman.

Last month, the Chinese e-commerce giant Alibaba Group said it was blackmailed by a magazine. The magazine, IT Time Weekly, was accused of asking for 300,000 yuan ($49,000) from Alibaba or it would run reports harmful to the e-commerce company.