German retail sales fell unexpectedly in December, dropping 1.4 percent on a monthly basis in real terms, preliminary data showed on Tuesday.

The notoriously volatile indicator was down 0.9 percent on an annual basis. Economists polled by Reuters had forecast retail sales to rise 0.9 percent on the month and 2.3 percent on the year.

November retail sales were revised downwards to a fall of 1.0 percent on the month, from a previously reported decrease of 0.9 percent. On an annual basis sales were also revised downwards to a gain of 0.9 percent from 1.4 percent.

(Reporting by Sarah Marsh and Gareth Jones)