A major outage at CommBank that had customers unable to access critical services such as online banking has been fixed, the bank says.

The cause of the outage is still unknown, but ACM understands the bank has ruled out a cyber attack.

The outage included CommBank banking services, including payments, online access and ATMs.

More than 7000 people reported the outage on DownDetector, a platform that tracks outages for various online services, at midday on October 2.

The bank's app was offline, and ATMs entered "standby mode" and could not give out cash or accept deposits.

Services were "restored" by 2.30pm on October 2, a Commonwealth Bank spokesperson advised.

"Some of our services were unavailable for approximately an hour before they started being restored," the spokesperson said.

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