Online shopping sites say they are finding it hard to keep up with demand for canned infant milk powder, after measures came into force at the start of the month to restrict people carrying the product from Hong Kong to the Chinese mainland.

From March 1, individuals arriving from Hong Kong were allowed to carry just two cans of infant formula. Hong Kong has already banned anyone there from buying 1.8 kilos of the product to crack down on cross-border trading and prevent stores from running out of stock. Violators face a fine of HK$500,000 ($64,500) and up to two years in jail.

Similar two-can purchase restrictions have also been announced by the Netherlands and New Zealand for milk powder there.