China's securities watchdog has vowed to take more efforts to prevent insider trading in mergers and acquisitions (M&A) deals.

Listed firms should submit a list of names with knowledge of the M&A deals once they file the initial plans with the stock exchanges. They should update the list when there are major changes to the deals or new information such as valuation and proposed pricing, the China Securities Regulatory Commission (CSRC) said on its website Monday.

If abnormal fluctuations in the companies' stock prices are spotted after the filing of the M&A plans, the stock exchanges could ask the firms to update the insider list, the CSRC said.

Insider trading in M&A deals are among the key market irregularities that the CSRC vowed to crack down on. In 2018, the regulator imposed a record-high amount of fines to forestall financial risks, with insider trading taking the lion's share of the penalized cases.