SHANGHAI - The Shanghai Stock Exchange has strengthened requirements on information disclosure to curb speculation, asking listed firms to be specific about announcements that could affect stock prices.

The Shanghai Stock Exchange said this week that it requires companies listed on the exchange to make detailed disclosures about risks and avoid overly positive statements about new share offerings, strategic agreements and name changes.

Such announcements tend to draw speculation and could be misleading to investors when company disclosures focus too much on positive effects, without due reminder about risks.

The Shanghai Stock Exchange also said listed companies tend to issue very general announcements regarding abnormal price swings. An amended rule for such filings will subject listed firms to more detailed disclosures.

A lack of a stringent information disclosure system has left many domestic investors, most of them retail investors, vulnerable to fraud and market manipulations.

China Securities Regulatory Commission also announced last week more than 2 billion yuan in fines for 12 price-rigging cases in China's A share market, causing many stocks that surged dramatically over the past few months to plunge toward the daily limit of 10 percent on Monday and Tuesday.

The Shanghai Stock Exchange also said that it will step up crackdowns on market irregularities, respond swiftly to problems that arise in the market and continue to improve information disclosure to warn of risk and encourage rational investing.