London, Nov 25 : Banking services giant HSBC has apologised after thousands of customers in the UK were unable to access mobile and online banking for hours during an outage on Black Friday. HSBC customers were unable to pay bills or make discounted Black Friday purchases online, reports the BBC. HSBC said it was "really sorry for the inconvenience". The bank said an internal system issue caused the disruption. "It is impacting HSBC UK customers only -- there is no impact to First Direct or M&S Bank customers," the bank said in a statement. 'We apologise for the continued inconvenience caused by the disruption to personal mobile and online banking. The issue stems from our internal systems, and we are working hard to get a fix in place,' the bank posted on X. Some other customers were unable to make card payments online, because they cannot verify purchases using the app. The exact number of people affected by the problems at the bank was unclear. HSBC has around 14.8 million customers across the UK. Social media users on X responded to HSBC UK's post on the platform with complaints. "I got paid today and cannot pay any bills! Sort it out HSBC," one user posted. /IANS