The Shanghai Stock Exchange (SSE) yesterday announced new rules for stock trading to prevent and curb irregularities.

The new rules, targeted mainly at "abnormal price fluctuations", are expected to curb insider trading, excessive speculation and price rigging, an SSE statement said. They will become effective from September 1.

The SSE will target stocks with limitless price fluctuation and will have the right to suspend them from trading for up to 30 minutes on a day they surge above 100 percent or drop below 50 percent of their opening prices.

The rule will be used to prevent excessive speculation on newly issued and debuting stocks, the SSE said.

Sichuan Changjiang Packaging Holding Co stocks jumped 491.9 percent the day they resumed trading after a four-and-half-month suspension. The SSE suspended its trading in the afternoon.

The second new rule is targeted at curbing insider trading. The SSE will have the right to suspend the trading of stocks that surge or drop dramatically for two consecutive days and if more than 30 percent of their total daily turnover comes from one branch office of a securities company.

The stocks can only resume trading at 10:30 a.m. on the day a company makes a formal clarification and if the authorities accept it.

This has happened with Hangxiao Steel Structure. Hangxiao's stocks rose 77 percent in six days leading up to March 13, when the company issued a statement to the SSE saying that it had signed a contract worth 34.4 billion yuan ($4.43 billion) for a construction project in Angola.

Incidentally, Hangxiao's turnover from Changjiang Securities' Hangzhou branch accounted for 33.74 percent and 64.7 percent of its total turnover on February 12 and February 13, the government watchdog suspicious and prompting it to investigate the issue.

The third rule will be used to curb investors' excessive speculation on penny worth stocks, the SSE said. Special treatment stocks, which are allowed a 5 percent daily fluctuation, can be suspended from trading if they touch the daily limit at close for three consecutive days.