Uniqlo operator Fast Retailing Co. Ltd. reported an unexpected decline in quarterly profit on Thursday, blaming warm weather for hurting winter clothing sales even as its Chinese business shrugged off concerns of a decelerating economy.

Uniqlo has become Asia's biggest clothing retailer, helped in part by the popularity of its basic items such as ultralight down coats and Heattech thermal underwear.

However, stores in Japan struggled to sell such items in October and November due to unseasonably warm weather, the company said.