United States stocks have fallen sharply as weak Chinese economic data and rising tensions in Ukraine offset solid US retail sales and labour-market data.
At the closing bell, the Dow Jones Industrial Average tumbled 231.19 points, or 1.42%, to 16,108.89.
The broad-based S&P 500 fell 21.86 points, or 1.17%, to 1,846.34, while the tech-rich Nasdaq Composite Index slumped 62.91 points, or 1.46%, to 4,260.42.
Stocks had opened higher following solid US reports on retail sales and jobless claims, but veered into negative territory mid-morning with the sell-off accelerating in the afternoon.
Analysts pointed to a range of factors behind the big drop, such as several disappointing bits of Chinese economic data that included an 8.6% growth in industrial output, the slowest rate of growth in five years.
"Each time US investors worry about China, it results in lower stock prices," Dan Greenhaus, chief global strategist of BTIG, said.
However, the Chinese data was released overnight and did not initially tilt the market into the red.
Other factors included news Russia had escalated military training exercises near Ukraine and congressional testimony from Federal Reserve vice chair nominee Stanley Fischer that confirmed his support of phasing out stimulus.
Mr Greenhaus said Thursday's trade should be seen in the context of a market that has not significantly gained since the start of 2014.
"We're basically flat for the year," he said.
"So you're talking about two and a half months of sideways action."