TOKYO • Fast Retailing Co, Asia's largest retailer, said hackers may have gained access to the personal information of about half a million users of its Uniqlo and GU brand e-commerce portals.

Hackers accessed at least 460,000 accounts registered on Fast Retailing's Japanese shopping websites, the company said in a statement on Monday.

Users' personal information, purchase history and parts of credit-card numbers may have been accessed, the Tokyo-based retailer said. The hacking occurred from April 23 to May 10, and the firm is investigating.

Consumer data security has become a growing concern for corporations as e-commerce proliferates, with an increasing number of retail and services companies reporting incidents.

Last year, Cathay Pacific Airways and Marriott International were among those reporting that hackers accessed customers' personal information.

Fast Retailing said the incident was limited to the Japan websites and the breach was a list-based attack. Such access can happen when customers use the same ID and password combinations on multiple websites. The company advised users to change their passwords.

Fast Retailing has been investing heavily to build up its e-commerce operation. Internet sales made up 10 per cent of domestic sales in the first half of the company's current fiscal year. It does not disclose the total number of online users.

Shares of Fast Retailing were down less than 1 per cent at 11.02am in Tokyo yesterday, while the benchmark Topix index slipped 0.9 per cent.

BLOOMBERG