Stocks fell on Friday, ending four weeks of back-to-back gains, as political instability resurfaced in Europe and investors braced for a confidence vote in Greece after U.S. markets close.

The Dow Jones industrial average was down 61.15 points, or 0.51 percent, at 11,983.32. The Standard & Poor's 500 Index was down 7.91 points, or 0.63 percent, at 1,253.24. The Nasdaq Composite Index was down 11.82 points, or 0.44 percent, at 2,686.15.

For the week, the Dow fell 2 percent while the S&P was off 2.5 percent and the Nasdaq lost 1.9 percent.

(Reporting by Ryan Vlastelica; Editing by Kenneth Barry)