TOKYO -- China's embassy in Japan on Tuesday called for an orderly evacuation of Chinese nationals from the areas worst hit by the catastrophic earthquake and ensuing damage to nuclear reactors.

The Chinese embassy has been making an all-out effort to rescue and help Chinese citizens affected by Friday's massive earthquake and resulting devastating tsunami, it said in an urgent notice posted on its website.

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The embassy was organizing the evacuation "due to the seriousness of and uncertainty surrounding the accident at the Fukushima nuclear plant at present," it said.

"We hope our compatriots in the worst-hit disaster areas remain calm, listen to instructions, understand and cooperate with the evacuation operation," the embassy said.

The embassy in Tokyo and the Chinese consulate in Niigata would send buses to four areas in Miyagi, Fukushima, Ibaraki and Iwate prefectures to pick up Chinese nationals and help them return home, according to the notice.

Earlier in the day, the Japanese government said levels of radiation released by damaged reactors at the quake-stricken Fukushima No. 1 nuclear power plant were high enough to threaten human health.

Four of the complex's six reactors have been damaged by explosions. Japan's nuclear safety agency has urged residents living around the nuclear power plant to stay indoors and avoid exposure to possible radioactive substances.