The European Union's statistics office Eurostat said month-on-month volumes of retail sales fell by 1.1 per cent in the 17 countries using the euro in May, with Germany reporting a fall of 2.8 per cent and Portugal dropping 3.1 per cent.
The month-on-month fall, which was broadly in line with the 1.0 percent dip economists polled by Reuters had expected, was blamed largely on a decline of 0.9 per cent in the non-food sector, such as sales of electrical goods and clothing.
The May figure represents a fall of 1.9 per cent from the same month last year, sharply lower than the Reuters consensus forecast of a 0.5 per cent year-on-year fall.
Month-on-month sales of food, drink and tobacco were down by 0.6 percent in the euro area in May.
Earlier this week, euro zone producer prices slipped more than expected as energy costs eased, leading some economists to predict that the European Central Bank may hold off on any further interest rate rises in the next few months after an expected hike this week.
Last week, the ECB signalled it would raise interest rates as consumer inflation in June stabilised well above the bank's target. The ECB's rate-setting Governing Council meets on Thursday.