China formally arrested 25 staff at the website of a prominent business newspaper and a linked publication on bribery charges Friday, as Beijing asserts greater control over the media.

They included Liu Dong, president of the 21st Century Business Herald's website, and its deputy editor.

The staff were accused of blackmail as well as offering and taking bribes, prosecutors in the commercial hub Shanghai said in a statement.

The practice of businesses paying media to run or delete stories is seen as widespread in China, and the wave of arrests at the paper, known for its aggressive investigative reporting, has raised fears of selective enforcement amongst liberal journalists.

The newspaper's editor Shen Hao, one of China's most respected liberal journalists, was shown on state-run television last month "confessing" to being involved in extortion.

It was the latest in a series of such confessions shown by state broadcaster China Central Television, and was condemned by some journalists and lawyers as violating Shen's right to a fair trial.

Authorities announced a nationwide campaign against media extortion earlier this year.

The drive comes at a time when China's government is exerting tighter controls over the media -- already one of the most restricted in the world.

Journalists have encountered increased censorship since China's President Xi Jinping came to power in 2012, with less space for liberal critics of the government to publish their views.

Publisher Xia Ri and editor-in-chief Luo Guanghui of Moneyweek, a publication affiliated to the Herald, were also among the 25 arrested, according to the statement.

The national business newspaper is part of the Southern Media Group, which is owned by the Guangdong provincial government, and is well respected among financial professionals.

Staff at the newspaper colluded with others to demand payments for positive news from listed firms and prominent companies, while publishing "malicious" attacks on those who refused to cooperate, state media previously reported.

Employees also threatened companies with negative coverage if they did not agree to place adverts or sign cooperation agreements for high fees, according to reports.

The crackdown on media corruption has also hit state media, with police in July detaining Rui Chenggang, a prominent financial news anchor for CCTV, for setting up a public relations company to receive payments in exchange for providing coverage.