Target Corp. (TGT), less than two weeks after disclosing a security breach of its credit- and debit-card system, said some customers have been unable to use its gift cards because they weren't fully activated.

"We are aware that some Target gift cards were not fully activated and apologize for the inconvenience," Molly Snyder, a spokeswoman for Minneapolis-based Target, said in an e-mail. Less than 0.1 percent of the cards sold during the holiday period were affected, Snyder said, adding that the company will honor the affected cards.

Target has been working to retain customer' loyalty after saying Dec. 19 that security for 40 million cards may have been compromised as shoppers made purchases in stores from Nov. 27 to Dec. 15. The company also said data related to shoppers' personal identification numbers was stolen. While the chain said it had identified and resolved the issue, the breach occurred during the most important period of the year for retailers and with shoppers already showing reluctance to spend.

Target rose 1.1 percent to $63.18 at 11:49 a.m. in New York. The shares climbed 5.6 percent this year through yesterday, compared with a 29 percent increase for the Standard & Poor's 500 Index.

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