A customer uses a Barclays ATM in central London, July 23, 2010. REUTERS/Andrew Winning

LONDON (Reuters) - Thousands of Barclays customers in Britain were unable to access their bank accounts or withdraw money from cash machines on Saturday after a system crash caused chaos nationwide.

The problems, which began at around 1:30 p.m. British time, hit telephone and online banking services and caused frustration at retail outlets as embarrassed shoppers were forced to abandon purchases at the till.

Barclays’ telephone banking centres were inundated with calls from customers, many of whom were angry at the lack of information. A Barclays spokeswoman was unable to elaborate on the cause of the problems.

“We became aware of a problem earlier in the day,” she said. “We apologise to customers for any inconvenience.”

At 8:15 p.m., access to online accounts was still being denied and calls to the helpline suggested the problems were ongoing.

Barclays is Europe’s sixth-biggest bank by market value. It signed a two-year deal with NCR Corp on Aug 16 for the management and maintenance of its UK network of ATMs.