KIRK HARGREAVES/STUFF

BNZ customers could not access ATMs, eftpos or mobile banking yesterday.

BNZ says customers who suffered financial loss after not being able to access their accounts on Saturday could be offered compensation.

For about three hours on Saturday BNZ customers were locked out of their accounts after a power cut in Australia triggered a system failure.

A BNZ spokesman said if customers suffered financial loss from the fault they could seek compensation from the bank.

"Each case will be examined on its merit," the spokesman said.

READ MORE: BNZ customers demand compensation; some might even get it

BNZ chief customer officer consumer and wealth Paul Carter said it was working with affected customers.

"We are also working through how best to support impacted customers," Carter said.

"This will include working with customers who experienced direct financial loss due to the outage to ensure they are not unfairly impacted.

"The outage was our mistake and we'll be working to make things right."

BNZ communications manager Cliff Joiner said the power cut happened in Melbourne at its parent bank National Australia Bank (NAB).

He did not know what caused the power cut or exactly where in Melbourne it happened.

"We outsource some of our systems to our parent," Joiner said.

BNZ's systems, including eftpos, online banking, and its ATMs, were out of action for over three hours, leaving customers frustrated at being unable to access money in their accounts.

NAB customers were also affected Australia-wide, he said.

NAB was looking at offering some customers compensation but BNZ had not made a decision on whether it would, he said.

"We're still assessing the full impact of yesterday's outage and the issue of compensation for BNZ customers hasn't been addressed yet."

He would not comment on whether BNZ had insurance for such situations.

When the power cut hit it took out "quite a few systems" at NAB and that impacted BNZ systems, he said.

The New Zealand fault was felt nationwide, but it was not known exactly how many customers were affected, he said.

"All we know is it was a significant failure and it impacted all of our services so eftpos, ATMs, mobile banking and internet banking were all affected.

"We're still looking into the cause."

Most services were operating by mid afternoon yesterday and there had been no problems reported since, he said.

"We apologise to all of our customers who were affected."

 - Stuff