In China, the Shanghai stock index plunged 8.5 percent Monday, its worst fall since 2007, despite government efforts to calm the market.
Teva Pharmaceutical Industries of Israel jumped 8 percent after saying it would buy Allergan's generic drug business. Allergan jumped 7.5 percent.
The Dow Jones industrial average lost 133 points, or 0.8 percent, to 17,435 as of 9:35 a.m. Eastern time.
