The Dow Jones Industrial Average decreased 368.03 points, or 1.05 percent, to 34,792.76. The S&P 500 was down 65.79 points, or 1.48 percent, to 4,393.66. The Nasdaq Composite Index shed 278.42 points, or 2.07 percent, to 13,174.65.
All the 11 primary S&P 500 sectors ended in red, with energy and communication services down 3.1 percent and 2.41 percent, respectively, leading the losses.
U.S.-listed Chinese companies traded lower, with all the top 10 stocks by weight in the S&P U.S. Listed China 50 index ending the day on a downbeat note.
At a panel discussion hosted by the International Monetary Fund on Thursday, Powell affirmed the U.S. central bank's determination to bring down inflation, indicating that a half percentage point rate hike is possible at the Fed's meeting next month.
The remarks came at a time when market worries over the pace of monetary tightening have increased.
According to the CME Group's Fedwatch tool, market expectations for a 50 basis point move in May rose to 97.6 percent on Thursday.
On the economic front, U.S. initial jobless claims, a rough way to measure layoffs, decreased by 2,000 to 184,000 in the week ending April 16, the Department of Labor reported on Thursday. Economists polled by the Wall Street Journal forecast initial jobless claims to total a seasonally adjusted 182,000.
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