American luxury specialty department store Neiman Marcus has become the second retailer after Target to have fallen victim to a cyber-security attack.

According to some security experts, the breach is related to the recent payment card information theft at Target.

Neiman Marcus Group spokeswoman, Ginger Reeder, said they were notified in mid-December by its credit card processor about potentially unauthorised payment activity following customer purchases at stores.

The department store could not estimate the number of affected, but said it is notifying the customers whose cards were used fraudulently.

McAfee security expert, Robert Siciliano, said it is possible that Neiman Marcus does not yet know the extent of the breach, and believes that the two thefts were likely committed by the same organised group.

"It’s a knee-jerk reaction that the security industry has right now," Siciliano added.

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Target, on the other hand, has disclosed that its massive data theft, which was previously believed to have affected 40 million customers, has now affected over 70 million customers.