Beijing police have arrested an environmental reporter and his associates in an apparent extortion scandal, as China works to crack down on corruption in the news media.

A string of corruption scandals in China's news media has shaken the faith of the public in the largely state-controlled industry and in response, the media regulator unveiled tougher rules last year.

The group's ringleader, surnamed Chen, is accused of blackmailing businesses into paying hundreds of thousands of yuan to delete embarrassing online reports about their activities on a website for environmental news, the official Xinhua news agency said.

Their tactics allegedly reaped more than 6 million yuan ($968,836) in profit, with victims ranging from the province of Shandong to far-flung Inner Mongolia, the agency said in an online report.

Chen, his wife and other relatives are suspected of laundering the money through a cultural broadcasting company they set up. He and four associates were arrested late last month, police said on Friday.

The government has vowed to crack down on extortion by journalists, but critics say it has also squeezed freedom of expression.

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