UK lender Nationwide Building Society's (POB_p.L) customers were unable to access online banking and a mobile banking app on Sunday after a scheduled overnight maintenance overran.
Nationwide spokeswoman Michelle Slade said that the online bank and mobile banking app were now back up and running.
"Unfortunately our overnight planned maintenance has overrun and is affecting customers accessing our online bank and mobile banking app," the customer-owned lender's spokeswoman said.
She said that customers could still use ATMs and make Visa card payments. "We apologise for the inconvenience caused to our customers," Slade said in a statement.
The customers of Britain's third-biggest provider of mortgage and savings products complained of the online banking glitch on social networking site Twitter.
One of the users said "Suggest nationwide building society should give better advance warning on site maintenance ...."
(Reporting by Aashika Jain in Bangalore; Editing by Lisa Shumaker)