RBS have apologised for inadvertently locking frustrated customers out of their online and mobile accounts.

Customers started reporting problems at around 5am on Friday with issues continuing for around five hours.

The issues also affected Royal Bank of Scotland. NatWest and Ulster Bank customers.

However, a statement issued later that morning by the bank announced that the problems had been resolved.

RBS chief executive Ross McEwan said the bank feels customers’ “pain” when problems with the system arise – but he added that such incidents were becoming less frequent.

The malfunctions are thought to have potentially stemmed from a firewall upgrade, but investigations remain ongoing.

The bank has sought to reassure customers by announcing that no client data was compromised at any point.

The latest disruption came just a day after Barclays customers were left struggling to log in. Those issues have also now been fixed.

A statement from RBS said: “We would like to apologise to customers who experienced issues logging into their online and mobile banking accounts this morning, this issue has now been resolved.”

The RBS banking group has nearly eight million customers who use mobile and online banking.

Telephone banking and ATMs were not impacted during Friday’s disruptions, however.

Earlier yesterday, McEwan told LBC: “We feel the pain for our customers every time this happens.

“We’re still working through what the issue is there...

“Absolute apologies to customers who are used to using mobile – and more and more are using mobile.”

He said: “We make a lot of changes to our technology on an ongoing basis – it may be related to that but we just don’t know at this point.”

Questioned about previous glitches, he said such incidents had “dropped dramatically”.

He said: “If you look back at 2014 we had something like 300 incidents, last year we only had 20, so we are certainly improving the organisation and how it operates for our customers.”

Customers on Twitter hit out at the bank, with one saying: “Natwest app down again. Not really acceptable for our 24 economy! How can we trust you with our money?”

The criticism follows an earlier announcement this month by RBS, who revealed plans to swing the axe on another 54 branches.

In the case of 1 of the forecast closures, the cutbacks mean that there are no other bank or building society branches in those areas.

The banking problems follow TSB’s huge IT meltdown earlier this year, after a botched IT switch saw millions of customers locked out

of accounts.

Banking customers are facing further disruption as HSBC has scheduled routine essential maintenance for tomorrow. Its mobile banking app and online banking will be unavailable for personal customers during the early hours of the morning.