Royal Bank of Scotland (RBS) customers have been unable to use the bank's mobile banking app today because of a spike in traffic.
Bank clients found themselves blocked from the app as they tried to check their balances in the run-up to the final weekend of the month.
The bank, who own Ulster Bank, said it had seen "record" numbers of people trying to access mobile banking and apologised to customers on Twitter, saying that "high traffic" was preventing some customers from being able to log in.
Ulster Bank have not confirmed if services for their customers have been affected.
It said: "We are currently experiencing record usage of our mobile banking app. Over 5,500 customers are logging on every minute."
We’re aware of some issues on our Mobile Banking service and are working hard to fix them. Sorry and thanks for your patience.— Royal Bank (@RBS_Help) February 28, 2014
The bank later said that services had resumed as normal.
If you’re having difficulty with our mobile app, online banking, telephone banking and ATMs are all working normally.— Royal Bank (@RBS_Help) February 28, 2014