The S&P 500 suffered its biggest daily drop since late September on Thursday as the European Central Bank disappointed market hopes for greater stimulus.
The ECB move triggered a spike in the euro that caught investors by surprise, forcing them to shift positions and that affected many asset classes. Bond prices dropped after the announcement.
At the same time, the CBOE Volatility index, the stock market's fear gauge, jumped 13.8 percent, closing at its highest since Nov. 17.
The ECB cut its deposit rate deeper into negative territory and extended its asset buys by six months, as expected. But some market participants had hoped for greater stimulus.
All 10 S&P 500 sectors fell in a second day of sharp losses for US stocks. Healthcare ended down 2.2 percent, leading the day's decline, followed by energy, down 2 percent.
"The biggest influence was the (ECB President Mario) Draghi talk this morning; it didn't satisfy the US markets," said Peter Tuz, president of Chase Investment Counsel in Charlottesville, Virginia.
Federal Reserve Chair Janet Yellen's comments signalled the Fed was on track to raise interest rates this month.
Yellen told lawmakers the US central bank was close to lifting its overnight interest rate from near zero. She gave an upbeat view of the US economy, as she did in remarks on Wednesday. The Fed's next policy meeting is on Dec. 15-16.
The Dow Jones industrial average fell 252.01 points, or 1.42 percent, to 17,477.67, the S&P 500 lost 29.89 points, or 1.44 percent, to 2,049.62 and the Nasdaq Composite dropped 85.70 points, or 1.67 percent, to 5,037.53.
The S&P 500 posted its biggest daily percentage decline since Sept. 28 and closed at its lowest since Nov. 13.
Volume was elevated in S&P 500 index options expiring on Friday, particularly in put options that suggest people were hedging against the possibility of losses, said Henry Schwartz, president of options analytics firm Trade Alert, in New York.
"After a really slow week it does look like hedgers are taking some action today," he said.
Data released on Thursday showed initial U.S. jobless claims for last week rose but remained at levels consistent with a strengthening labor market. Friday's employment report is expected to show the U.S. economy added 200,000 jobs in November.
Zafgen shares were down 5.1 percent at $5.96 after the company said the U.S. Food and Drug Administration was putting on complete hold a late-stage study testing its experimental obesity drug.
Declining issues outnumbered advancing ones on the NYSE by 2,518 to 579, for a 4.35-to-1 ratio on the downside; on the Nasdaq, 2,159 issues fell and 674 advanced for a 3.20-to-1 ratio favoring decliners.
The S&P 500 posted 9 new 52-week highs and 26 new lows; the Nasdaq recorded 53 new highs and 78 new lows.
About 8.2 billion shares changed hands on US exchanges, compared with the 6.8 billion daily average for the past 20 trading days, according to Thomson Reuters data.