A bad day in the financial markets was made worse by an apparent trading glitch, leaving traders and investors nervous and scratching their heads over how a mistake could send the Dow Jones Industrial Average into a 1000-point tailspin.
At its afternoon low, the Dow Jones Industrial Average had plummeted 998.50 points, its biggest intraday point drop ever. The swing from its intraday high was 1010.14 points.
The markets were already on edge before the midafternoon collapse as traders watched televised scenes of rioting in Athens following the Greek government's approval of its portion of the European Union and International Monetary Fund bailout.
Throughout the day, markets around the globe posted big declines as investors reacted with disappointment to the failure of the European Central Bank to signal any heightened concern about the spiraling Greek debt crisis.
The Dow eventually rebounded to close down 347.80 points, or 3.2%, at 10520.32, its worst percentage decline since April 2009.
Standard & Poor's 500-stock index dropped 3.2% to 1128.15 Bond, commodity and currency markets were all roiled as investors fled from risky assets toward the safety of gold and Treasurys.
The Chicago Board Options Exchange Volatility index, or VIX, which tracks volatility in stock-index options, at one point soared 60% to nearly 40 and ended the day up nearly 32%.
