"We are aware that customers are now experiencing issues logging into their online and mobile banking accounts".
"We are aware that customers are experiencing issues and are working to fix it".
The RBS outage on Friday also affected NatWest, RBS's most highly rated brand among customers.
Commenting on the Barclays outage, Lev Lesokhin, SVP strategy & analytics at software vendor Cast, said United Kingdom banks seem to be unusually vulnerable to such glitches, which are often due to software failures.
NatWest is a subsidiary of RBS, which also posted on Twitter to say it was "aware of some issues on our Digital and Mobile Banking services and working hard to fix them".
Meanwhile customers of online challenger bank Cashplus - which targets people with poor credit histories - were unable to access their accounts, make cash withdrawals, or make or receive payments earlier this week.
The banking group has almost eight million customers who use mobile and online banking. Telephone Banking and ATMs are available. "We feel the pain for our customers every time this happens", he said.
The problem was initially thought to be a glitch affecting only NatWest customers, but it later emerged that there were issues across the RBS banking group.
"Absolute apologies to customers who are used to using mobile - and more and more are using mobile". But we just don't know at this point.
Mr McEwan insisted that the number of such incidents had "dropped dramatically" from 300 IT-related interruptions in 2014 down to 20 a year ago, and that his team was working "flat out".
NatWest customers took to social media to complain about the issue, saying they would be unable to pay their bills or access their money. Not really acceptable for our 24 economy! How can we trust you with our money?'
Earlier this month, RBS announced plans to swing the axe on another 54 branches, 14 of which are the last bank in town - meaning there are no other bank or building society branches in those areas.
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