Police are investigating the hacking of Hongkong Post's EC-Ship online portal, after Hongkong Post on Tuesday confirmed that hackers had stolen customers' personal information on Sunday and Monday.

In a statement, Hongkong Post said hackers had retrieved senders' and recipients' names, addresses, phone numbers, fax numbers, and email addresses during the cyberattack.

It said it had now sent emails to all affected account holders, reminding them to remain vigilant.

Hongkong Post made the announcement a day after it confirmed the attack, when it said it had blocked the hackers, and that police and other authorities had been informed. It also said EC-Ship was running as normal.

It insisted it has been following established government procedures on information and cybersecurity, adding it would fully cooperate with the police investigation.