Hong Kong - US banking giant Citigroup said Thursday that computer hackers have accessed information in about one percent of accounts held by its US credit card card customers.
"During routine monitoring, we recently discovered unauthorized access to Citi’s Account Online. A limited number - roughly one percent - of Citi bankcard customers’ account information... was viewed," it said in a statement.
A Citigroup spokesperson in Hong Kong told AFP that the security breach affected credit card accounts in the United States, but said she could not say how many customers had been affected.
"There has been no impact on any of our Asia-Pacific customers - it's just in the US," she added.
Citi is one of the industry's largest providers of credit cards with more than 21 million accounts generating more than $77bn in receivables in North America according to its 2010 annual report.
It was not immediately clear how the hackers got at the information.
The New York-based bank said hackers didn't gain access to customers' social security numbers, dates of birth, card expiration dates or card security codes.
Citi also said it was contacting customers whose information was viewed and has implemented procedures to prevent a recurrence of the security breach.