Orient Securities' mainland-based clients with trading accounts in its Hong Kong unit will be banned from buying stocks and transferring in funds starting on Wednesday. Guotai Junan International Holdings, the overseas unit of Shanghai-based Guotai Haitong Securities, issued a similar notice earlier, stating that onshore investors could no longer add stock holdings through their overseas accounts starting this week. This follows a regulatory crackdown that began months ago with fines on Tiger Brokers and Futu Securities International.