Shanghai - China's securities regulator is tightening its rules against insider trading by executives of state-owned listed firms.

The tougher approach comes after some senior executives sold shares in their companies in larger numbers or at a faster pace than allowed by the rules, the China Securities Journal said, citing an unnamed securities oversight official.

"The agency has looked into the violations and taken regulatory action accordingly," said the official from the China Securities Regulatory Commission (CSRC), without elaborating.

"The board of directors of listed firms should correct any such wrongdoing immediately," the official warned.

The oversight body has drafted new rules to better regulate the trading of equities in listed firms by senior company executives, the newspaper said.

It did not provide details about the new regulations which will be released soon but added that a technology platform and operating system that will provide oversight has been completed.

Most of China's listed firms were once state-owned and in many the state still retains a controlling stake.

Current regulations stipulate that top company officials must not transfer more than a quarter of their total shareholdings in their firm in each year of their tenure.

Executives are also subject to a one-year lock-up period after the listing of the firm's shares and cannot transfer stock in the company within half a year of stepping down from their post.

If officers who own five percent of a listed firm carry out a transaction within six months after buying or selling, the gains they make will belong to the company.