Wall Street closed lower on Friday but still kept a robust October, with the Dow hitting best month since 2002, the S&P hitting best month since 1987.
The Dow Jones industrial average tumbled 276.10 points, or 2.26 percent, to 11,955.01. The Standard & Poor's 500 slumped 31.79 points, or 2.47 percent, to 1,253.30. The Nasdaq Composite Index dropped 52.74 points, or 1.93 percent, to 2,684.41.
For the month, the market turned out to be one of the best months for stocks. The Dow rallied almost 10 percent in October, the best monthly performance since October 2002. The S&P 500 and Nasdaq surged about 11 percent, the biggest climb since December 1991 and September 2010 respectively.
Euro zone hopes and strong earnings optimism seemed to be fragile. Investors were concerned about Italy, the euro zone's third largest economy, which is also facing a debt problem. Japanese monetary authorities announced earlier Monday a massive currency intervention to safeguard the country's exporters. The greenback surged significantly after the intervention.
Investors also were worried that the U.S. economy, especially the exporting sector will be hurt by strong dollar.
Meanwhile, the securities firm MF Global filed for bankruptcy protection on Monday after the company's debt was downgraded to junk status by ratings agencies which were concerned about its large holdings of European government debt, which added to concerns of the magnitude of the problem in Europe.
Adding to the pressure, the Organization for Economic Cooperation and Development warned on Monday that European economies will see a "marked slowdown" next year.
With optimism about the resolution to the European debt problems starting to fade away, investors decided to take profits after a strong October.
Also on the economic front, investors will be focused on the meeting of the Federal Reserve's policy-setting committee. While the committee is expected to maintain Fed fund rates unchanged, investors will be closely watching for any clues the Fed may give on the outlook of the economy.
As for dollars, the greenback soared on Monday after Japan's latest intervention.
U.S. oil price edged down on Monday also due to Japan's massive intervention. Light, sweet crude for December delivery dropped 13 cents, or 0.14 percent to settle at 93.19 dollars a barrel on the New York Mercantile Exchange. But it still posted the biggest monthly gain of 17.66 percent in more than two years.
In London, Brent crude for December delivery last traded flat around 110 dollars a barrel, on track to post a 6 percent monthly gain, the biggest increase since April.