Stocks fell sharply on Thursday with all three major indexes breaking through their 50-day moving averages in a sign of waning upward momentum as concerns over the economy weighed.

The Dow Jones industrial average <.DJI> was down 191.78 points, or 1.57 percent, at 12,021.31. The Standard & Poor's 500 Index <.SPX> was down 21.61 points, or 1.64 percent, at 1,298.41. The Nasdaq Composite Index <.IXIC> was down 50.61 points, or 1.84 percent, at 2,701.11.