Customers trying to log in to online banking through the NAB app received the error message: "Sorry, something went wrong. Couldn't connect to internet banking."

The bank advised customers to log in using an internet browser instead, however some customers reported this still didn't work.

UBank, a division of NAB, was also brought down by the outage, which began at around 5pm.

Customers attempting to log on were served the message: "Internal server error".

The outage also affected the bank's "contact centre", where customers can speak to a customer service representative over the phone, and is thought to have affected the processing of some payrolls.

Some customers posted photos on social media that they had been on hold for more than an hour as they waited to speak to someone from the bank.

Others said they had no way to buy food, while one man said he was overseas with no access to his money.

NAB and UBank both apologised to their customers on Twitter on Tuesday evening and said services would return as soon as possible.

"We're currently experiencing issues with some of our services - sorry about this," NAB said.

"We're working to get back online & we'll keep you updated."

UBank wrote: "We apologise for technical problems across our contact centre [and] internet banking."

All services appeared to return to normal at around 9pm. An NAB spokeswoman apologised to those affected and said the bank worked to fix the issue as soon as possible.

"We apologise to our customers for the inconvenience caused."

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