Stocks extended losses on Wednesday as doubts rose about the effectiveness of the European Central Bank's massive funding operation to tackle the region's debt crisis.

The Nasdaq also was dragged lower by Oracle Corp which fell more than 13 percent, trading near $25.00.

The Dow Jones industrial average <.DJI> was down 76.21 points, or 0.63 percent, at 12,027.37. The Standard & Poor's 500 Index <.SPX> was down 8.50 points, or 0.68 percent, at 1,232.80. The Nasdaq Composite Index <.IXIC> was down 52.09 points, or 2.00 percent, at 2,551.64.

(Reporting By Angela Moon; Editing by Chizu Nomiyama)