"Workers' efforts at the risk of their lives have made the situation progress little by little," Kan was quoted as saying.

Kan's reported comments came as engineers at the stricken nuclear plant on Monday raced to fix disabled cooling systems and restore power, as fire trucks sprayed water to help cool reactor fuel pools.

The cooling systems designed to protect the plant's six reactors from a potentially disastrous meltdown  were knocked out by the March 11 tsunami that followed a 9.0 magnitude earthquake, and engineers have been battling rising temperatures.

In the biggest nuclear crisis since Chernobyl in 1986, the plant was last week hit by explosions and fires and has released radiation into the atmosphere, with levels around the facility highly dangerous.