The pan-European STOXX 600 index fell 0.7 percent with most major country indices well in the red on returning from the May Day holiday.

Germany's DAX, which outperformed through most of the day, closed flat as software firm SAP weighed.

Madrid's IBEX fell 1.6 percent.

US Fed Chairman Jerome Powell disappointed the doves on Wednesday, signaling little appetite to adjust interest rates anytime soon.

"That was interpreted as somewhat more hawkish than expected given that the market has been pricing in a reduction perhaps as early as this year," said Ken Odeluga analyst at City Index.

"Investors see the need to recalibrate their expectations because the chair said there was no greater bias for a cut or a raise in the near term."

SAP fell 1.3 percent and weighed the most on STOXX 600. Security researchers said up to 50,000 companies running SAP software are at greater risk of being hacked.

The basic resources sector dropped 1.6 percent after copper prices fell to their lowest in more than two months.

Andritz was among the biggest decliners on STOXX 600 after the Austrian engineer cut its full-year profit forecast, partly in response to weak car industry demand that hit its metals business.

Consumer stocks slipped on online-only fashion retailer Zalando's 3.3 percent fall after it announced plans to charge delivery fees for small orders in more markets.

Helping temper those losses, German drugmaker Bayer was the biggest boost to the pan-region index after the US Environmental Protection Agency said that glyphosate, the key ingredient in Bayer's Roundup weed killer, is not a carcinogen.

This contradicts decisions by US juries that found it caused cancer in people and led to thousands of lawsuits against Bayer.

Carmaker Volkswagen jumped 3.7 percent as shrugged off a 1 billion euro legal charge and met first-quarter operating profit forecasts.

But other auto stocks such as planemaker Airbus and its supplier Safran slipped. Euro zone factory activity contracted for a third month in April, data showed, hurt by weak global demand.

Shares in Swiss toilet and plumbing supplies maker Geberit vaulted to the top of STOXX after first-quarter earnings beat expectations.