Dangerous levels of radiation began leaking from a crippled nuclear plant Tuesday, forcing Japan to order 140,000 people to stay indoors.
The news sent Japan's benchmark Nikkei 225 stock average down more than 1,000 points, or 11 percent. The index fell 6 percent Monday.
In the U.S., Dow Jones industrial average futures are down 260 points, or 2.2 percent, at 11,663 ahead of the opening bell. Standard & Poor's 500 index futures are down 33 points, or 2.6 percent, at 1,258. Nasdaq 100 index futures are down 64, or 2.8 percent, at 2,226.
Oil prices are down $3.95 at $97.22 as traders anticipate lower demand in the aftermath of the earthquake.