In midday trading in New York, the Dow Jones industrial average was down 0.2 percent to 8,750.28 and the broader Standard & Poor's 500 index fell 0.6 percent to 939.23.
Germany's DAX closed 0.7 percent lower at 5,069.24, while the CAC-40 in France lost 0.4 percent at 3,326.14. The FTSE 100 index of leading British shares was down 0.5 percent at 4,441.95, with Barclays PLC falling 4 percent after it confirmed the sale of its global investment unit to U.S. fund manager BlackRock Inc. for $13.5 billion.
"This was, of course, far from being a surprise, and the weakness seen in the share price of Barclays is a reflection of investors taking money off the table when it comes to the banking sector in general," said David Jones, chief market strategist at IG Index.
In Europe, stocks fell after the European Union's statistics office Eurostat revealed that industrial production in the 16 countries that use the euro slumped by 1.9 percent in April from the previous month. That was more than the 1 percent decline expected in the markets and stoked worries that the recession in the euro zone may not yet have bottomed out, as some had hoped.