NAB customers back online after experiencing phone and internet banking outages

NAB has confirmed it has been affected by an online banking outage. (ABC News: Keana Naughton)

National Australia Bank (NAB) has seen most of its services restored, after experiencing a digital outage across multiple platforms.

In a statement, an NAB spokesperson said: "Some business customers are continuing to experience login issues via NAB Connect, and we're working as quickly as possible to resolve the remaining impacts.

"We apologise to customers for the disruption and thank them for their patience and understanding while we continue to restore services."

Across Thursday afternoon, NAB's outage impacted its internet banking, the NAB mobile app and phone lines.

One NAB customer said she received an alert on her mobile banking app which said: "We're sorry, the app isn't working at the moment. We'll have it back up and running as soon as we can."

A customer's screenshot of the NAB outage notification. (Supplied)

Another customer, Jessi Nokes, said she became aware of the outage about 1:30pm AEST, when she was out shopping.

Ms Nokes said she could still pay for her items but was unable to log in to her mobile banking account.

She was finally able to regain access to her online banking about 4:20pm AEST.

NAB's website said: "Our team is working to fix this as soon as possible. We apologise for the inconvenience."

No detail has been provided as to what caused the outage, but NAB's website said no planned maintenance was scheduled.