Fears that Greece's troubles could spread through the global financial system shook markets on Monday, driving U.S. stocks to their worst day of the year. Investors fled from stocks in Europe and the U.S. and retreated to the safety of government bonds.

For the day:

The Dow Jones industrial average fell 350.33 points, or 2 percent, to 17,596.35.

The Standard & Poor's 500 index lost 43.85 points, or 2.1 percent, to 2,057.64.

The Nasdaq composite dropped 122.04 points, or 2.4 percent, to 4,958.47.

For the year:

The Dow is down 226.72 points, or 1.3 percent.

The S&P 500 index is down 1.26 points, or 0.06 percent.

The Nasdaq is up 222.41 points, or 4.7 percent.