Citigroup resolves 'technical issue' that left accounts frozen

Customers had taken to social media to complain about the outage, which affected several U.S. states, including New York, Pennsylvania and California, according to Bloomberg.

"We experienced a brief technical issue that is now resolved," Citigroup's customer service Twitter account said in response.

Bloomberg reported the news of the outage first.

A Bloomberg reporter spoke with four people at a bank branch on Manhattan's Upper East Side who said debit cards did not work at the ATM there. (http://bloom.bg/296tSVr)

Citigroup was not immediately available for further comment.

The bank's shares had closed down 9.4 percent at $40.30 on Friday, as Britain's vote to exit the European Union sparked the biggest global financial shock since the 2008 crisis.

(Reporting by Anya George Tharakan in Bengaluru; Editing by Sandra Maler)