The Dow and S&P 500 extended losses on Wednesday, dropping nearly 3 percent after a sharp snap-back rally in the last session as investors fretted about the economy and high levels of public debt.

The Dow Jones industrial average tumbled 328.66 points, or 2.92 percent, at 10,911.11. The Standard & Poor's 500 Index was down 32.41 points, or 2.76 percent, at 1,140.12. The Nasdaq Composite Index slid 71.77 points, or 2.89 percent, at 2,410.75.

(Reporting by Ryan Vlastelica)