The clampdown on price rigging and other irregularities in the stock market will be intensified, the head of the market watchdog said yesterday.

Speaking at the first China Listed Companies Seminar, Shang Fulin said that price rigging activities include spreading rumors about asset injections and back-door listings to jack up share prices.

"Listed companies, which have already become a main engine of economic growth, need to increase transparency in their business activities, including restructuring and mergers and acquisitions," the chairman of the China Securities Regulatory Commission (CSRC) said.

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The CSRC recently penalized Hangxiao Steel Structure for violating information-disclosure rules. Three people have been detained for their alleged roles in insider trading in shares of the construction company.

The securities regulator also fined the company 400,000 yuan ($52,600) for failing to abide by information-disclosure rules, the first such case since rules on information release by listed companies took effect on January 30.

The Shanghai Stock Exchange announced it will suspend the accounts of investors involved in irregular trading.

Shang also spoke of plans for healthy market development. "We will continue to promote the establishment of new markets for different classes of companies, including a second board for small- and medium-sized companies," he said.

Shang encouraged listed companies to induct foreign strategic investors to be more competitive on the international market.

By the end of 2006, the total capitalization of the 1,474 listed companies reached 24.5 trillion yuan ($3.2 trillion) with accumulated net profits hitting 378.1 billion yuan ($50 billion) that year.