Official figures show that retailers in the euro zone saw their sales increase by a disappointing 0.1% in August, after 0.4% growth the previous month.
Over the year to August the retail sales index gained 1%, the EU's Eurostat agency said. Economists had forecast a monthly rise of 0.2%.
Eurostat at the same time revised its July retail sales figures higher to a monthly rise of 0.4%, compared with the previous 0.1% rise.
In August the food, drinks and tobacco sectors posted a rise of 0.2% from July, while the non-food sector recorded a fall of 0.1%.
