The privacy watchdog said on Tuesday that a data breach involving the South China Athletic Association (SCAA) may affect about 70,000 people.

The Office of the Privacy Commissioner for Personal Data (PCPD) said it was investigating the matter.

The sports club announced on Monday night that it was subject to a cyberattack, but that there was no evidence of personal information being leaked.

The PCPD said the case may involve data including names, ID card and passport numbers, addresses, phone numbers, dates of birth, photos and e-mail addresses.

"The PCPD appeals to the affected persons to make enquiries or complaints with the relevant organisation or the [office] if they suspect that their personal data have been leaked," it said in a statement.

The privacy watchdog said it's asked the SCAA to notify those affected as soon as possible.

The PCPD called on people to be careful about potential theft of personal data and consider changing passwords and activating the multi-factor authentication feature of online accounts.

They're also urged to check their bank statements for unauthorised transactions and be more cautious with e-mails and phone calls received.

The SCAA said it's sorry about what happened and has since taken steps to protect the data of its members.

"The SCAA sincerely apologises to the affected members. We will spare no effort to strengthen our cybersecurity to ensure our members’ personal data are safely protected and restore their trust in us," it said in a statement.