Qantas is contacting customers after a cyber attack targeted their third-party customer service platform, BBC reported.

On 30 June, the Australian airline detected "unusual activity" on a platform used by its contact centre to store the data of six million people, including names, email addresses, phone numbers, birth dates and frequent flyer numbers.

Upon detection of the breach, Qantas took "immediate steps and contained the system", according to a statement.

The company is still investigating the full extent of the breach, but says it is expecting the proportion of data stolen to be "significant", according to BBC.