The Tokyo Stock Exchange's key Nikkei average plunged 5 percent Tuesday to its lowest level in more than three years as the failure of the U.S. securities firm Lehman Brothers Holdings Inc. spooked investors.

The benchmark gauge fell 605.04 points, or 4.95 percent, from Friday to 11,609.72, its lowest close since July 8, 2005, when it ended at 11,565.99.

The Topix, which covers all first-section issues, was down 59.63 points, or 5.07 percent, to finish at 1,117.57.