"There is no mistake that this is a level that can have an effect on humans," the Japanese prime minister, Naoto Kan, said in a televised address.
All but 70 or so engineers trying to stabilize the plant were told to leave after the explosion and fire in reactor No4, and a blast in reactor No2.
"Please do not go outside. Please stay indoors. Please close windows and make your homes airtight," the chief cabinet secretary, Yukio Edano, told them.
The Tokyo governor, Shintaro Ishihara, was forced to apologise yesterday after suggesting the devastating toll was "divine retribution" for egoism in Japanese politics.