BEIJING — The Chinese securities watchdog on May 27 published stricter rules on the selling of stocks of major shareholders as such activity had triggered market volatility and stoked the concerns of retail investors.

The new policy improved regulation on stock reductions through block trading, selling of non-public offering shares, information disclosure, and equity transfers via agreements.

It came only one day after the China Securities Regulatory Commission (CSRC) said it has planned the revision to curb massive and irregular stock-selling of major shareholders.

“The improved system will guide major shareholders to reduce holdings in a standard, reasonable and orderly manner, which will help stabilize market expectations and shore up investors’ confidence,” said the CSRC.

The Shanghai and Shenzhen exchanges also released detailed rules shortly after the regulator’s move on May 27.

For those who hold more than 5 percent of a company’s stakes, their sales of non-public offering shares should not exceed 50 percent of their total holdings in a 12-month period after unlocking. Stocks transferred through block trading should not surpass 2 percent of a company’s total shares in 90 days, and the transferees are not permitted to sell again within six months.

Major shareholders, supervisors and management should report and publicize their holding reduction plans 15 trading days in advance.

Deng Ge, CSRC spokesperson, stressed that the detailed rules must be followed and the commission will take restrictive measures against violations and irregular transactions.

The new rules took effect on Saturday.

The CSRC vowed continued efforts to act against false information disclosure, insider trading and market manipulation during stock-selling by major shareholders.