Stocks ended lower on Friday, capping off their worst month in over a year as a downgrade by Fitch Ratings of Spain's credit rating reignited worries about euro-zone debt issues.

The Dow and S&P 500 registered their worst monthly percentage losses since February 2009.

Based on the latest available data, the Dow Jones industrial average <.DJI> fell 122.36 points, or 1.19 percent, to end unofficially at 10,136.63. The Standard & Poor's 500 Index <.SPX> was down 13.66 points, or 1.24 percent, at 1,089.40. The Nasdaq Composite Index <.IXIC> was down 20.64 points, or 0.91 percent, at 2,257.04.

For the month, the Dow was down 7.9 percent, the S&P was down 8.2 percent and the Nasdaq was down 8.3 percent.

For the week, the Dow was down 0.6 percent, the S&P was up 0.2 percent and the Nasdaq was up 1.3 percent.

(Reporting by Caroline Valetkevitch)