The sell-off in US stocks accelerated in late afternoon trade Monday as a global rout resumed after Wall Street equities had earlier shown signs of rallying.
Near 1925 GMT, the Dow Jones Industrial Average was at 15,771.57, down 688.18 points (4.18 percent).
The broad-based S&P 500 fell 90.08 (4.57 percent) to 1,880.81, while the tech-rich Nasdaq Composite Index dropped 209.10 (4.44 percent) to 4,496.94.
US stocks opened sharply lower Monday and have been in the red all day. However, the market pushed closer to even at midday thanks in part to gains by Dow members Apple and Intel and some smaller companies.
But both Apple (-2.9 percent) and Intel (-1.4 percent) were back into negative territory as part of a broad market retreat. The deepest losses on the Dow included Cisco Systems (-5.5 percent), JPMorgan Chase (-5.0 percent) and UnitedHealth (-5.4) percent.
Peter Cardillo, chief market economist at Rockwell Global Capital, said the latest wave of selling was due to margin calls that forced some investors to liquidate holdings to raise cash.
US stocks have d ropped four straight days as worries about an economic slowdown in China have spurred selling in global equity markets.
On Monday, the Shanghai index plunged 8.49 percent, while bourses in England, France and Germany were all off more than four percent.
The steep equity declines added to talk that the US Federal Reserve was now likely to push back a plan to raise interest rates until later in 2015, or 2016.