Stock indexes extended declines on Friday, with the Dow industrials down 3 percent as investors fretted over discord within the European Central Bank over how to deal with the region's sovereign debt crisis.

Traders also cited angst about possible terror acts over the weekend as a reason to sell. Ceremonies will be held in New York and across the United States to mark the 10th anniversary of the September 11 attacks on the World Trade Center and the Pentagon.

The Dow Jones industrial average <.DJI> dropped 330.96 points, or 2.93 percent, to 10,964.85. The Standard & Poor's 500 Index <.SPX> dropped 33.40 points, or 2.82 percent, to 1,152.50. The Nasdaq Composite Index <.IXIC> dropped 63.87 points, or 2.53 percent, to 2,465.27.

(Editing by Leslie Adler)