The selloff in U.S. stocks accelerated on Tuesday, as the Dow and S&P 500 dropped for a fifth day, with the pullback coming on the cusp of earnings season.

The slide marked the S&P 500's worst day since December 8. The declines were the largest losses this year in terms of both points and percentage drops for each of the three major U.S. stock indexes.

All S&P 500 sectors ended solidly lower, with industrial and materials names suffering the biggest drops. About 80 percent of shares listed on the New York Stock Exchange and the Nasdaq Stock Market ended lower.

The major U.S. stock indexes each fell more than 1.5 percent, pushing the S&P 500 below its 50-day moving average of 1,372.30, an area viewed as a significant support level that will make or break the current uptrend.

Dropping below that level suggests a loss of momentum, and it looks pretty widespread, said Katie Stockton, chief market technician at MKM Partners in Greenwich, Connecticut, who added that the S&P 500 could fall to about 1,350 before finding a new level of support.

The Nasdaq also slid below its 50-day moving average and closed below 3,000 for the first time since March 12.

Concerns about European debt have resurfaced and could be a catalyst for further declines as the yields on riskier Italian and Spanish debt climbed. U.S.-listed shares of Banco Santander fell 3 percent to $6.51.

Dow component Alcoa Inc climbed 5.4 percent to $9.82 in extended trading after the aluminum maker reported its quarterly results.

With 5 percent of the S&P 500 components having already reported, profits are seen rising 3.1 percent in the quarter, according to the Thomson Reuters Director's Report.

We've clearly seen a major slowdown in earnings, which are dependent on global growth now that profit margins have stopped expanding, and global growth isn't great right now with all the issues in Europe, said Jim McDonald, chief investment strategist at Northern Trust Global Investments in Chicago, which has about $650 billion in assets under management.

The Dow Jones industrial average <.DJI> lost 213.66 points, or 1.65 percent, to 12,715.93 at the close. The Standard & Poor's 500 Index <.SPX> dropped 23.61 points, or 1.71 percent, to 1,358.59. The Nasdaq Composite Index <.IXIC> tumbled 55.86 points, or 1.83 percent, to 2,991.22.

Volume was higher than average, with about 8.18 billion shares traded on the New York Stock Exchange, the American Stock Exchange and Nasdaq, above last year's daily average of 7.84 billion.

The CBOE Volatility Index <.VIX> jumped 8.4 percent to 20.39, and was up for the eighth straight day, its longest streak of consecutive gains in nearly nine years. At its session high, the VIX touched 21.06 - up almost 12 percent for the day.

The Standard & Poor's 500 Index is still up 8 percent so far this year - compared with its gain of 12 percent at the end of the first quarter.

But the benchmark index has fallen 4 percent in the past five sessions, its worst streak since November, as investors questioned the economy's strength and the U.S. Federal Reserve's inclination to keep easy money flooding into the market.

Friday's soft U.S. payrolls report added to the U.S. stock market's recent losses that were sparked by last Tuesday's minutes from the Fed's March policy meeting. The Fed's minutes were interpreted as showing the central bank was less than keen to launch more stimulus.

A Reuters poll on Monday showed most major Wall Street banks expect anemic growth in the U.S. job market and a struggling economic recovery to force the Fed to undertake another round of monetary stimulus.

Apple shares dropped quickly from hitting a new high of $644 per share to briefly top a $600 billion market capitalization. Its stock later fell to trade down 1.2 percent at $628.44 at the close.

Supervalu Inc shares jumped 15.2 percent to $6.13 after the third-largest U.S. supermarket operator reported better-than-expected earnings and issued a full-year profit forecast above Wall Street's view.

Best Buy shares hit their lowest since December 2008 and were at their session low after Chief Executive Brian Dunn resigned after 28 years with the world's largest consumer electronics retail chain. The stock fell 5.9 percent to $21.32, not far above the intraday low of $21.21.

(Editing by Jan Paschal)

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