A technical problem left customers at the U.K.'s largest bank unable to make purchases or withdrawals using their payment cards on Sunday.

A Lloyds Banking Group (LLDTF) spokeswoman said the three-hour outage had been resolved but did not know how many customers had been unable to use their cards.

Issues with in-store purchases were resolved by 6 p.m. local, and ATM outages were resolved by 7:30 p.m. At 7:45 p.m. local, the bank's customer service hotline was still warning callers "we're extremely busy at the moment" because the bank was "experiencing issues with some credit cards and debit card transactions."

One bank executive took to social media, directly answering customer complaints and questions. He said the outage was caused by a server failure.

"My apologies to TSB customers having problems with their cards. I'm working hard with my team now to try to fix the problems," wrote Paul Pester. He is CEO of TSB Bank, which split off from Lloyds in September but is one of several banks that he tweeted "use the same IT systems."

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The banking group has suffered other payment outages, including one when the two banks split and divvied up their retail locations and customer accounts.