BEIJING, June 13 -- The government will implement new rules starting next month to keep stock manipulators and those engaged in other illegal activity out of the mainland's stock markets.

"Those breaking the rules will be banned from trading on the stock markets for three to five years," the China Securities Regulatory Commission (CSRC) said in a statement.

CSRC said those who cause particularly heavy investor losses as a result of their illegal action will be banned from the markets for five to 10 years.

The regulator didn't say what illegal activity the new rules target.

The statement said the new rules will take effect from July 10.

In recent years, the government has stepped up its efforts to clean up and modernize the country's securities markets and attract more investors.

A CSRC official said two weeks ago the country's listed companies will adopt international accounting standards next year and improve their information disclosure.

Some analysts said rumors of the ban may in part explain the sharp fall of domestic stocks Wednesday, when the Shanghai Composite Index dropped 5.33 percent, posting its biggest decline in more than four years.

The market had already been consolidating for the past three sessions on concerns liquidity will dry up as more large State-owned companies launch initial public offerings.

(Source: Shenzhen Daily/Agencies)