"We're sorry for the inconvenience".
"If there was a loss this morning driven by the outage today, yes compensation will be provided to customers", she said during a press conference on Saturday.
"We're aware of an issue with some merchant terminals that connect to the Optus network".
"We've had an outage in terms of time - we know that that looks like - but we don't know the extent of the impact on individual customers at this time".
The outage affected internet and mobile banking, ATMs and EFTPOS and is believed to have started about 8am AEST.More news: How the EU's new GDPR law gives people more power online
NAB confirmed that it suffered a nationwide systems failure as a result of power being cut to its mainframe.
NAB customers have been unable to access their accounts with the bank suffering an outage to its online, mobile, EFTPOS and ATM services.
The outage comes at an awkward time, with Australian banks under pressure from a probe that's exposed a decade of unethical practices by the lenders, including lying to regulators, falsifying documents and taking bribes to extracting fees from dead customers.
"We just saw $2500 walk out the door". You guys are making billions of dollars each year while us small businesses are losing money because customers are unable to pay for their groceries. But "sorry this happened on a Saturday", makes me feel all warm and fuzzy inside.More news: "Spygate" Has Comey and Clapper in the Cross-hairs
"We still don't know the number of customers that are impacted", she said.
Craig Daniell, co-owner of Kingfisher Seafoods at Melbourne's Camberwell Market said the outage would cost him a fair slice of profit.
Twitter user @lachy_1234 responded: "Not good enough".
Of the Twitter speculation that inevitably followed the outage, perhaps the most cogent suggestion for the chain of events came from Conor Stokes, who suggested: "I imagine this scenario: 1) the main online transaction processing server fails somehow 2) fail over to the hot replica doesn't work 3) your phone system goes down because it queries your online transaction processing server for account queries".
Customers of NAB-owned BNZ in New Zealand faced similar problems.More news: Italian premier-designate quits over nixed anti-euro minister