Stocks extended losses on Thursday, with the S&P 500 hitting session lows amid global economic worries and turmoil in the Middle East, and as traders cited a report of Saudi police firing on protesters.

The Dow Jones industrial average <.DJI> dropped 219.93 points, or 1.80 percent, to 11,993.16. The Standard & Poor's 500 Index <.SPX> lost 23.69 points, or 1.79 percent, to 1,296.33. The Nasdaq Composite Index <.IXIC> slid 48.84 points, or 1.77 percent, to 2,702.88.

(Reporting by Chuck Mikolajczak)