A passenger walks to the First Class counter of Cathay Pacific Airways at Hong Kong Airport in Hong Kong, China April 4, 2018. REUTERS/Bobby Yip/File Photo

HONG KONG (Reuters) - Hong Kong's privacy commission on Thursday expressed serious concern over a data breach at Cathay Pacific Airways 0293.HK and urged the airline to notify passengers affected by the leak as soon as possible and explain the details.

Shares of Cathay slid more than 6 percent early on Thursday, a day after it said data of about 9.4 million passengers of Cathay and its unit, Hong Kong Dragon Airlines Ltd, had been accessed without authorization.