Locals in some areas outside the 20- km radius of the crippled Fukushima No. 1 nuclear power plant will have to be evacuated due to accumulating radiation, Japan's top government spokesman Yukio Edano said Monday.

People living within 20 kilometers around the plant already have been ordered to leave because of concerns about radiation. Other people within 30 kilometers radius had been advised to stay indoors.

Edano said, however, that residents of five communities, some more than 30 kilometers from the plant, are being urged to leave within a month, as high radiation levels have been detected in some places and there are concerns about long-term health risks.

He also said residents of another five localities should be prepared to evacuate in case of emergency.

Thousands of people remain missing and workers are still struggling to regain control of the crippled nuclear power plant one month after a devastating earthquake and tsunami hit northeastern regions of Japan on March 11.