NAB has promised to refund its customers who lost money after the bank had a four-hour outage today that left people without access to ATMs, EFTPOS and online banking.

The bank’s business executive general manager Cindy Batchelor said they would look to refund customers who were put out by the glitch.

“If there was a loss that was driven by the outage today, then compensation will be provided to customers,” she said.

“We’ll work with each and every one of them to understand exactly what happened to that particular customer.”

NAB announced via Twitter about 1.30pm that its ATMs, EFTPOS and online banking services were back online following the lengthy outage.

The Commonwealth Bank also reported issues with “some merchant terminals that connect to the Optus network”.

They issued an apology to customers and said they were “working hard” to restore services.

NAB customers and businesses were left unable to access bank accounts and use EFTPOS machines today after the bank’s online services went down.

NAB’s Chief Customer Officer of Business and Private Banking, Anthony Healy, issued a video apology on Twitter, saying “On behalf of the executive team and everyone here at NAB, I want to apologise for the outages that you were experiencing this morning with your banking services.

“I want to apologise to those who were out trying to do their shopping on a Saturday morning and particularly our merchants who are trying to do business and maintain banking services for their customers. We’re sorry and it’s not good enough.”

He assured customers that NAB has its “best and most experienced team on it” and they were working to get things up and running as soon as possible.

Earlier, NAB issued an apology on social media, telling customers they should be able to use their cards on non-NAB operated machines. “Sorry this happened on a Saturday everyone. Systems are still affected but for purchases only, NAB customers can use non-NAB operated EFTPOS machines, but are unable to withdraw cash.”

The outage affected internet and mobile banking, ATMs and EFTPOS and is believed to have started about 8am AEST.

The post has received frustrated replies from clients, some of whom claim the outage is “killing” their businesses.

“We just saw $2500 walk out the door. But ‘Sorry this happened on a Saturday’ makes me feel all warm and fuzzy inside,” one Twitter user replied.

Another wrote: “Sorry ain’t good enough. 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. Will we be getting compensated???”

Craig Daniell, co-owner of Kingfisher Seafoods at Melbourne’s Camberwell Market said the outage would cost him a fair slice of profit.

“We’ve had easily 100 customers who couldn’t buy their produce this morning,” he said.

“There’s been quite a few angry customers; it’s been a massive inconvenience.”

Mr Daniell said most customers use cards to pay for their produce.

“It’s impacted us big time, 80 per cent of our sales are on card now ... out here in Camberwell they don’t use cash,” he said.

“Saturday is our busiest day, you rely on Saturday sales to balance out the rest of the week.

“My wife is very upset, when you pay a lot of fees to the bank it gets very frustrating.”

Meanwhile, Eastgate Chiropractic Clinic in Perth, has asked clients to bring cash to pay for their appointments.

There are reports HICAPS (for healthcare claims) machines were also experiencing issues, but are now up and running again. HICAPS is operated by NAB and includes Medicare and Worksafe Victoria payments.

NAB customers and businesses have expressed embarrassment and frustration over the issue when people were left unable to pay for purchases.

Twitter user Kurt Hoffman asked: “NAB, what’s happening? All ATMs and EFTPOS machines saying NAB is unavailable?”

Naresh Gupta tweeted, “This is very unfortunate ... I had this embarrassing experience when both my debit cards were declined at an EFTPOS machine. Never expect (sic) this from such a big bank.”

“This doesn’t just impact @Nab customers,” another Twitter user wrote. “I just had to pay for a $70 taxi ride in cash because the cabbie’s pay machine is on NAB. Who even carries cash these days?”

Some customers have reported they have been able to tap and pay with their credit cards.

According to reports, the NAB outage is impacting services Australia wide.

The bank has apologised for the inconvenience, and said it was working on rectifying the situation as soon as possible.

Customers of NAB-owned BNZ in New Zealand are also experiencing problems.

It is the latest in a series of recent tech glitches. Commonwealth Bank customers seemingly had their credit histories and mortgages wiped after glitch in April, while telco Telstra has suffered a number of outages leaving customers unable to make and receive calls.