Though Eurostat, the EU's statistics office, confirmed its previous estimate that the 17-country euro zone grew by 0.8 percent in the first quarter, analysts said the breakdown of the figures points to slower growth. They said a sharp rise in investment and construction output is unlikely to continue into the second quarter.

With consumption levels muted and governments across the region ready to put a brake on their spending to get public finances into shape, the main ingredients of growth could disappear, they noted.

In Germany, separate figures showed industrial output fell 0.6 percent in April while exports fell 5.5 percent on the month, clear signs that the euro zone's largest economy may be slowing down.

Germany led the way in the first quarter with a stunning 1.5 percent growth rate. Its high-value exporters in particular benefited from the rebound in global trade, but the figures Wednesday suggested that will not be sustained.

"With various leading indicators of activity having already softened somewhat in recent months, our guess is that growth will be materially slower in the second quarter," said Jonathan Loynes, senior European economist at Capital Economics.

"As such, hopes that continued strong economic growth in the euro zone will help to address the region's fiscal crisis are likely to fade fairly quickly," he added.

Despite signs of a slowdown and Europe's ongoing debt crisis, the markets are still pricing in the probability that the European Central Bank will follow up April's first interest rate in nearly three years with another in July as it tries to bring inflation back toward target.

Consumer prices in the euro zone are rising at an annual rate of 2.7 percent. That's above the ECB's mandate to keep inflation just below 2 percent.

The ECB is expected to keep its benchmark rate unchanged Thursday at 1.25 percent but indicate that another increase will be delivered in July.