Westpac has apologised for taking “too long” to fix a major tech outage that left thousands of customers unable to use digital banking from Monday night to Tuesday morning.

Some customers posted that they were “stressed” or “freaking out” when they could not access their accounts, saw “zero balances” or had their cards erased.

Shoppers were left red-faced as they were forced to abandon their purchases at the till, or were unable to pay their bills.

The problem affected mobile and online banking services and seemed to have occurred after a “routine technology upgrade”, Westpac confirmed.

The bank released an update 5am Tuesday (AEDT) saying its digital services were “restored and running as usual”.

“We want to apologise to all our customers who were impacted by the issue overnight,” said a statement on X.

“We recognise this took too long to resolve and we thank customers for their patience.”

According to outage website DownDetector, more than 10,000 people reported problems accessing their accounts on Monday.

The bank released its first statement about 9pm Monday, acknowledging its customers were “experiencing issues” accessing their accounts.

Updates were issued at 10.40pm and 11.48pm on Monday: “Our mobile and online banking services remain unavailable following a routine technology update earlier this evening.

“We’re still working to restore services for our customers and apologise for this experience.”

Some customers posting on X said they could not see their accounts after logging in to the bank’s mobile app.

Users trying to sign in on the bank’s website were met with the message “Westpac Online Banking is currently unavailable”.

One Westpac user posted on X that customers were seeing “zero balances or no bank accounts” and were “quite understandably freaking out now, thinking they have just lost their entire savings”.

Another posted to social media: “Why was an SMS or email not sent? My aunt and dad were very stressed out when … her accounts vanished … don’t use social media.”

Tweet from @mimiinbayside

A mum said she had to abandon her trolley at the supermarket while shopping with three kids when she was unable to transfer money to pay for the groceries.

“Toast for dinner it is …. no wonder why people are moving to crypto,” she posted.

-with AAP