Stocks fell on Wednesday as protests in Spain and Greece over euro zone austerity measures raised fresh concerns over Europe's ability to get its debt crisis under control.

The Dow Jones industrial average <.DJI> fell 43.96 points, or 0.33 percent, to 13,413.59. The S&P 500 <.SPX> dropped 8.26 points, or 0.57 percent, to 1,433.33. The Nasdaq Composite <.IXIC> lost 24.03 points, or 0.77 percent, to 3,093.70.

(Reporting by Caroline Valetkevitch; Editing by Chizu Nomiyama)