The customers of at least six Australian financial institutions were experiencing issues with payments and banking on Thursday, as investigations continued into the root of the problem.

The bank access issues appeared to start on Thursday morning, with customers reporting they couldn't properly access their banking apps.

ABC News was able to confirm at least six banks were impacted: Ubank, Bank Australia, Defence Bank, Beyond Bank, People's Choice and P&N Bank.

All six institutions had notes up on their websites about the issues as of late Thursday afternoon, however, some of those notes had been removed by mid-evening.

A Ubank spokesperson told the ABC that Ubank's systems were being restored and customers could now use their apps and online banking, including Osko payments, as of 9pm AEDT.

"Our teams are continuing to monitor this closely. As our app and online banking platforms come back up online, we'd like to thank our customers for their patience throughout the day and apologise again for the inconvenience caused," the spokesperson said.

Osko is a payment service from Bpay that allows banking customers to make automatic transfers to other accounts.

Other banks also apologised for the issue throughout the day, with Bank Australia's website note also urging its customers to be careful when making payments.

"As we continue to investigate issues with our app and internet banking performance, some customers may see successful payments highlighted as failed and payments take longer to arrive at their destination," read the note, which has since been removed.

"We ask customers to look closely at their accounts prior to resubmitting payment to avoid duplicates."

The ABC contacted the so-called Big Four major banks for comment.

NAB confirmed it had not been experiencing issues, while none of the other banks had prominent banners on their websites informing customers of banking issues.