Euro zone retail sales were weaker than expected in March, data showed on Wednesday, turning negative on a monthly basis for the first time since last September.

The European Union's statistics office Eurostat said retail sales in the 19 countries sharing the euro fell 0.8 percent month-on-month for a 1.6 percent year-on-year rise.

Economists polled by Reuters had expected only a 0.7 percent monthly fall and a 2.4 percent annual increase.

The decline in sales came despite a sharp improvement of sentiment both among consumers and in the retail sector in March, as measured by the European Commission's monthly economic sentiment survey.

A 2.7 percent monthly drop in the volume of automotive fuel seemed to have the biggest downward impact on the headline number, followed by a 0.8 percent decline in the volume of sales of non-food products.

Retail sales in the euro zone's biggest economy Germany fell 2.3 percent month-on-month in March and were 0.3 percent lower in the second biggest France.

In year-on-year terms in the euro zone, a 0.7 percent fall in petrol sales partially offset a 3 percent rise in the sales of non-food products.