MELBOURNE - Australia's second-largest telecommunications firm Optus, owned by Singtel, on Saturday ran a full-page apology in major newspapers for a "devastating" cyber attack 10 days ago and pointed affected customers to a new help site.

"We're deeply sorry that a cyber attack has happened on our watch," the company said in the notice.

"We know this is devastating and that we'll need to work hard to regain your trust," it said.

The new page on the company's website offered support to customers whose data has been breached, including how to replace drivers' licenses, passport and healthcare card numbers.

The company has agreed to pay the cost of replacing passports of compromised customers, Prime Minister Anthony Albanese said on Friday.

"We will be in touch with customers who have had their passport document number exposed," Optus said on its website.

Australian police said on Friday they had set up an operation to beef up protection of more than 10,000 Optus customers whose identity credentials had been shared online due to the data breach.

The authorities have declined to comment on their investigation and effort to find the hacker since the telcoms giant on Sept 22 first reported the theft of data of up to 10 million accounts, equivalent to 40 per cent of Australia's population. REUTERS