The issue, which has now been resolved, seemed to affect only customers attempting to log in through the website on both desktop and mobile devices.

A notification on NAB’s website indicated that “internet banking isn’t operational at the moment”.

“We apologize and are doing everything possible to restore the service,” the notification stated.

“You can still use the NAB app or Telephone Banking.”

The outage tracking site, Down Detector, observed a surge in outage reports, with thousands surfacing since 11am today.

NAB’s banking app remained functional.

“NAB Internet banking is back online and customers can login as normal,” a NAB spokesperson said.

“All other services, including the NAB mobile app, telephone banking, ATMs and other services have remained available to customers as normal.

“We’re sorry for any inconvenience this caused our customers.”