Moscow, April 12 (IANS/RIA Novosti) The Japanese government has assigned the maximum severity level to nuclear accident at the crippled Fukushima nuclear power plant, the Kyodo news agency said Tuesday citing government sources.

The maximum, seventh level on the International Nuclear and Radiological Event Scale (INES) is described as a "major event" and leads to "a major release of radioactive material with widespread health and environmental effects."

So far, the seventh level had been assigned only to the 1986 Chernobyl disaster.

The disaster was earlier classified as a category five event, or an "accident with wider consequences," which leads to a "limited release of radioactive material".

Japan's Fukushima nuclear power plant was damaged by a magnitude-9 earthquake and tsunami that hit Japan March 11.

Fukushima's operator has since been struggling to stop radioactive leaks from the plant's crippled reactors.

Chief Cabinet Secretary Yukio Edano said Monday, residents in areas between 20 and 30 km around Fukushima would be advised to evacuate due to accumulated radiation exposure levels.

Despite growing concern of radioactive fallout on the Russian territory, the Russian emergencies ministry said that radiation levels in Russia's Far East remained within the norm and ranged from 11 to 16 micro roentgen per hour Tuesday.