US coffee retail chain Starbucks has said that sales at company-operated stores open at least a year rose 11% in December compared to the year-ago period.

Seattle-based Starbucks said that based on strong revenue results for October, November and December, the company now expects earnings for the first quarter to 28 December to be between 25 and 26 cents per share. The company's previous forecast was for earnings of around 24 cents a share, compared to 20 cents a share in the year-ago period.

Starbucks also raised its full-year earnings guidance to a range of 84 to 87 cents per share, compared to a previous target of between 83 and 85 cents per share.

The company said its international chain of cafes had expanded to 7,567 in December, reported Reuters.