Published Friday, 06 December 2013
In a statement on the RBS website, the banking group blamed hackers for the problems.
"Due to a surge in internet traffic deliberately directed at the NatWest website, customers experienced difficulties accessing some of our web sites today," it said.
"This deliberate surge of traffic is known as a distributed denial of service (DDoS) attack. We have taken action to restore the affected web sites. At no time was there any risk to customers.
"We apologise for the inconvenience caused."
The disruption is understood to have lasted for about 30 minutes.
It comes after unconnected issues earlier this week, when hundreds of thousands of customers could not use their debit or credit cards for several hours.
The two incidents are not said to be in any way related.
© UTV News