Thousands of HSBC customers in the UK have been unable to access online and mobile banking services, preventing them from authorising online card purchases on Black Friday.
Customers began complaining about the outage at around 07:00 GMT, with thousands reporting issues on the Downdetector website.
Just before 11:00, the bank posted on Twitter: "We’re really sorry if you’re impacted by a disruption to Online and Mobile Banking right now. If you’re not able to authorise an online card purchase via the app, you can opt for a one time passcode via SMS. We’ll share updates here."
As of 13:20 no further update had been provided on what HSBC says is "an internal system issue".
Sam Richardson, deputy editor, Which?, says: "This HSBC outage will cause a real headache for a lot of its customers. In the worst cases it could prevent people making essential payments such as rent and bills, but it also falls on Black Friday, one of the busiest shopping days of the year."
Update: As of 19:00, the issue has still not been fixed: