The securities market regulator and police are cracking down on suspected violations of stock dealing rules and the fabrication of trading information, the latest step in a slew of measures to clean up markets amid wild exchange gyrations.

Police are investigating eight employees of the country's largest brokerage, CITIC Securities Co Ltd, for suspected illegal securities trading, the official Xinhua News Agency said on Tuesday.

In a statement to the Hong Kong stock exchange on Wednesday, CITIC Securities said it had not been informed of a probe into staff and the business was operating normally. An employee and a former employee of the China Securities Regulatory Commission are suspected of insider trading and forging official documents and seals, the agency said.

Wang Xiaolu, a reporter at business magazine Caijing is suspected, along with others, of fabricating and spreading false securities and futures trading information, the agency said. Police summoned Wang on Tuesday night, Caijing said in a statement on Wednesday, but it was not given a reason for his detention. It would support actions taken by Wang within the normal course of business, it said, adding it believed objective reporting promotes the healthy growth of the securities market.

In stock exchange statements on Tuesday, four Chinese brokerages said the CSRC was investigating them for failure to properly identify clients. Haitong Securities Co Ltd, Founder Securities Co Ltd, Huatai Securities Co Ltd and GF Securities Co Ltd said the CSRC was looking for failures to review and verify client identities, in line with rules.