China's securities regulator has pledged to crack down heavily on insider trading by limiting trading in stocks trade and stake transfers of listed firms suspected of conducting market manipulation.

The stock regulator will immediately suspend trading of public companies in cases where abnormal stock-price movements are detected, the China Securities Regulatory Commission said in a Website statement late Sunday.

The shares will resume trading only when firms clarify sufficiently market rumors affecting them or disclose price-sensitive information, the CSRC said in the statement.

"Under the current market scenario, manipulation and insider trading have replaced the falsification of profits by listed firms as the main illegal activity," the regulator said. "The CSRC will adopt more active and effective measures to deal with the crimes in a timely manner."

The CSRC will treat coldly applications for mergers and acquisitions by listed companies which are suspected of insider trading if they can't prove they are not linked to any manipulation, according to the statement.

Public companies and controlling shareholders are not allowed to replace exchange filings with other forms of information disclosures such as press conferences and media releases, the statement said.

Listed firms, their executives and shareholders mustn't offer personal opinions to the public when the companies are under regulatory probe for possible rule violation, according to the statement.

Chinese mainland shares have more than tripled in value since the beginning of 2006 as capital continuously flowed from citizens' savings into the nation's two stock markets.

The CSRC this month launched probes into several listed firms, whose shares had soared before the firms unveiled price-sensitive information. The regulator said it would severely punish persons involved in suspected insider trading.

The Shanghai Stock Exchange investigated 97 irregular share transactions, including 18 by mutual funds, in the first quarter of the year, equivalent to 35 percent of last year's total, as volatility in share prices rose.