U.S. stocks fell for the fourth day in a row as concerns about global economic weakness intensified, even as Federal Reserve Chair Janet Yellen reiterated her confidence in the U.S. economy.

Financial stocks fell hardest Thursday as investors worried that interest rates in the U.S. and elsewhere would remain low and sap bank profits. Oil prices sank again, this time to their lowest levels since 2003.

While all three major U.S. indexes finished lower, they recovered somewhat from far steeper losses earlier in the day.

The Dow Jones industrial average fell 254 points, or 1.6 percent, to close at 15,660. The Standard & Poor's 500 index fell 22 points, or 1.2 percent, to 1,829. The Nasdaq composite fell 16 points, or 0.4 percent, to 4,266.