European stocks were also dropping as investors grappled with mixed messages from the Federal Reserve. Recent Fed speakers have hinted interest rates could go up as soon as next week, but after European trading closed on Monday, the central bank's Gov. Lael Brainard said the lack of inflation pressure means "the case to tighten policy pre-emptively is less compelling."

The Dow industrials on Tuesday finished nearly 260 points lower as equities suffered a sharp sell-off amid a slump in energy shares and uncertainty about the Federal Reserve's plans for monetary policy. A decline in crude-oil prices, as the International Energy Agency warned of slowing growth in demand, also helped to fuel the downdraft for the stock benchmarks.

Asian shares were broadly mixed Wednesday on weakness in U.S. equities and continued worries that global central banks will soon reverse their easing schemes. In Japan, banks were particularly hard hit Wednesday on speculation that the Bank of Japan will reduce its purchases of superlong bonds to steepen the yield curve, while maintaining the negative rate on excess reserves.