Stock indices traded higher ahead of the European Central Bank's (ECB) interest rate decision. Analysts expect the central to keep its interest rate unchanged at 0.05%.

The Greek debt crisis remained in focus. The European Commission President Jean-Claude Juncker meets Greek Prime Minister Alexis Tsipras in Brussels on Wednesday. Juncker is expected to provide details of a proposal designed to avert a Greek default.

Meanwhile, the economic data from the Eurozone was better than expected. Eurozone's unemployment rate fell to 11.1% in April from 11.2% in March. It was the lowest level since February 2012.

March's figure was revised down from 11.3%.

Analysts had expected the unemployment rate to remain unchanged at 11.2%.

Retail sales in the Eurozone rose 0.7% in April, in line with expectations, after a 0.6% fall in March. March's figure was revised up from a 0.8% drop.

The increase was driven by higher food, drinks and tobacco sales, which rose 1.3% in April.

Gasoline sales were up 0.6% in April, while non-food sales increased 0.3%.

On a yearly basis, retail sales in the Eurozone rose 2.2% in April, beating forecasts of a 2.0% gain, after a 1.7% increase in March. March's figure was revised up from a 1.6% rise.

The annual rise was driven by non-food sales, which gained 3.3%, and by gasoline sales, which increased 3.2%.

Markit's and the Chartered Institute of Purchasing & Supply's services purchasing managers' index (PMI) for the U.K. fell to 56.5 in May from 59.5 in April, missing expectations for a fall to 59.2. It was the lowest level since December 2014.

A reading above 50 indicates expansion in the sector.

The decline was driven by a lower increase in new business.

Current figures:

Name Price Change Change %

FTSE 100 6,928.98 +0.71 +0.01 %

DAX 11,379.19 +50.39 +0.44 %

CAC 40 5,015.73 +11.27 +0.23 %