Tokyo stocks tumbled 3.14 percent Wednesday as a rout in Chinese equities hammered sentiment and added to losses fuelled by fears over Greece's future in the eurozone.

The Nikkei 225 index at the Tokyo Stock Exchange dropped 638.95 points to close at 19,737.64, the first time it has fallen below the psychologically important 20,000 level in several weeks.

The broader Topix index of all first-section shares dived 3.34 percent, or 54.75 points, to 1,582.48.