BEIJING / TOKYO - Premier Wen Jiabao urged Japan on Tuesday to provide prompt information on the nuclear crisis and quickly implement preventive measures to alleviate the consequences on neighboring countries during a phone conversation with Japanese Prime Minister Naoto Kan.

A man is tested for radiation exposure in Koriyama, Fukushima prefecture, northern Japan, on Tuesday. Koriyama is located about 70 kilometers from the crippled Fukushima nuclear plant. Japan expanded the evacuation zone around the nuclear plant on Monday because of high radiation levels. [Photo/Agencies]

The conversation took place after Japan raised the crisis level, from 5 to 7, at its crippled nuclear plant on Tuesday, a severity on par with the 1986 Chernobyl disaster.

Level 7 is the highest rank set by the International Nuclear Event Scale, which means huge quantities of radiation have contaminated a wide area.

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Wen called for Japan to strictly adhere to related international laws, take preventive measures, and promptly and accurately inform China on the latest updates.

He also said China is willing to strengthen cooperation in disaster relief and post-disaster reconstruction with Japan, adding that he wanted to "promote healthy and stable Sino-Japanese relations".

Kan said that, on behalf of the Japanese government and people, he expressed his sincere gratitude to China for immediately sending an international rescue team and offers of aid to the tsunami-devastated area.

He also expressed his gratitude to President Hu Jintao for paying a condolence visit to the Japanese embassy in Beijing, Xinhua reported.

While expressing regret for the accident at the Fukushima Daiichi nuclear power plant, Kan said Japan would promptly provide accurate information to the international community, including China, on the nuclear crisis.

The Japanese nuclear regulator told reporters on Tuesday that the raising of the severity rating from level 5 to 7 was based on new assessments of radiation leaks from the plant and that radioactive substances could affect human health and the environment.

But the agency emphasized that while the new ranking signified the radiation volume was equal to level 7, it was only one-tenth of the contamination released from Chernobyl into the atmosphere.

"Level 7 does not necessarily represent the extent of the damage, but indicates the amount of radiation released," Chen Zhuzhou, a researcher at the science and technology committee of the China National Nuclear Corporation, told China Daily.

Japan's Nuclear and Industrial Safety Agency (NISA) also stressed the difference between Chernobyl and Fukushima.

NISA spokesman Hidehiko Nishiyama said the acute radiation exposure at Chernobyl killed 29 people in contrast to Fukushima, where no fatal casualties were reported. He added that the reactors in the Fukushima plant retained their shape and were damaged by hydrogen explosions, unlike Chernobyl where the nuclear reactor itself exploded.

But Edano also reassured reporters that, so far, there was no "direct" damage to human health.

Youhei Hasegawa, a senior official at Japan's Meteorological Agency, said on Tuesday afternoon that a magnitude 6.3 quake which jolted northeastern Japan was one of the aftershocks. Parts of northeastern Japan were getting seismically active and more aftershocks were likely.

China Daily - Agencies