Stocks and interest rates tumbled after signs of slowing economies spooked traders who were already uneasy about a recovery.
"The markets reacted to a number of things, indicating a worldwide slowdown in the economy," NPR's Yuki Noguchi said.
A drop in Asian markets touched off selling after an index that forecasts China's economic activity was revised lower. In Europe, interbank lending tightened, placing the region's financial sector on shaky ground.
The losses intensified after news that U.S. consumer confidence fell this month because of worries about the economy. The Conference Board's Consumer Confidence Index dropped by nearly 10 points.
All of that underscored fears of a "double dip" recession, Noguchi said, including concerns that federal stimulus funds from last year are starting to peter out without creating significant private-sector job growth.
The Dow Jones industrials are down 268 points at 9,870. The Standard & Poor's 500 index is down 33 at 1,041. The Nasdaq composite index is down 85 at 2,135.
Only about 260 stocks rose while 2,800 fell on the New York Stock Exchange. Volume came to 1.6 billion shares compared with 925 million Monday.