The deal, signed late last year, hasn't been approved because the regulator suspected some managers at GF illegally profited by buying Yan Bian shares before the transaction was made public, the magazine said.

After Caijing reported on GF's case, six domestic brokerages issued clarifications to weed out the possibilities of imminent back-door listings after rumors bolstered shares of some firms believed to be their takeover targets.

"It's certain more regulatory probes into stock-related crimes will land this year with a focus to combat against insider trading and share-price manipulation," said a second source in Shenzhen.

"The watchdog is also finalizing a series of rules to prevent insiders such as big shareholders or company executives from profiting due to their information advantages."

Stock authorities are drafting rules to prevent senior executives from selling more shares of their listed companies than allowed, the Shanghai Securities News reported on Thursday, citing unnamed sources.

The stock watchdog will work with exchanges and the clearing agency to monitor company officials' investment activities while placing technical restraints to curb potential misconduct, the report said.

In another attempt to curb possible insider trading, the stock authority may issue rules to demand listed firms to hold public bidding for private stock placements with an aim to bring in strategic or financial investors.

Private placements involving controlling shareholders at listed firms will likely face tougher scrutiny and higher information-disclosure requirements, the Securities Times reported last week.

Regulators have noted that stock-price fluctuations increased during the process of some stock placements at listed firms while disputes over asset valuation have grown more intense recently, the report said.

"Authorities hope to curb misconduct in all aspects by bolstering oversight of listed firms, big shareholders as well as brokers," said the first source.

"As the market boom continues, tough crackdown measures will constantly pop up."

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