Investors may find out how Hong Kong’s stock market will react to mainland China’s crackdown on illegal cross-border securities trading on Tuesday, as Citic Securities estimates an impact on as much as HK$250 billion (US$31.9 billion) of assets in the city, a negligible amount for the third-largest stock market in Asia.

The sweeping campaign may affect between HK$150 billion to HK$180 billion worth of assets owned by mainland Chinese investors with Hong Kong stock accounts at Futu Securities International, Tian Liang, chief financial analyst at Citic Securities, said in a note on Sunday. Between an estimated HK$45 billion and HK$50 billion of similar assets at Tiger Brokers could also be affected, he said, totaling around HK$250 billion worth of assets in Hong Kong when including amounts from other brokerages, such as Long Bridge Securities, which were affected by the crackdown, according to the report.

Affected assets may include stocks and other types of securities, such as cash, money-market funds and options, and the total amount may diminish somewhat if any traders change the identities on the brokerages in order to legalise their Hong Kong accounts, according to Tian.

“The short-term impact of the new rules on the Hong Kong market is manageable,” he said in the report.

Monday is a public holiday in both Hong Kong and the United States.

The China Securities Regulatory Commission (CSRC) made an abrupt move on Friday to punish Futu, Tiger Brokers and Long Bridge for offering mainland Chinese investors trading access to overseas stocks without licenses. Gains from the unlicensed trades were confiscated by the regulator at all three organisations, and they were given two years to clean up the accounts, during which time stock buying would be prohibited and only selling would be allowed.

The move marks an escalation in a campaign that began at the end of 2022, when the CSRC first focused on unlicensed trading by banning Futu and its peers from adding new clients on the mainland.