London: Payment details of up to 40 million credit cards have been stolen after they were used in the stores of U.S. retail giant Target.
The retailer said it was investigating the matter after discovering that thieves had gained access to its payment systems.
According to the BBC, the thieves stole data between Thanksgiving and 15 December, Target said.
The attackers are believed to have been stealing credit card details for almost three weeks.
Target said thieves had taken credit card numbers, names, expiration dates and security codes for the cards, the report said.
It urged people who shopped at its stores to check credit card records and query unusual activity.
It is not yet clear how the attackers managed to get their malicious program on to point-of-sale equipment in the stores, the report said.
The US Secret Service, which has official responsibility for investigating financial fraud, was looking into the breach, it added.