The level of radioactive iodine in the sea off Japan's damaged Fukushima Daiichi nuclear power plant is 3,355 times the legal limit, the Japanese nuclear safety agency said, Jiji press reported Wednesday.

On Sunday, the level of radioactive iodine (iodine-131) measured 1,850 times the legal maximum a few hundred metres offshore, while its amount was 1,250 times the limit on Saturday, which clearly shows the speed of radioactivity growth.

Japanese officials are still denying that the current level of radiation poses an immediate threat to marine life or to seafood safety, the AFP news agency reported.

Experts assessed that the ocean should dilute radioactivity and limit sea flora and fauna contamination. It is still not known, however, how radioactive substances reached the sea in the first place.

Controlling leakage from the plant could take weeks or months, making precise risk assessments very difficult, Reuters reported.

Radiation from the crippled plant in northeast Japan went into air, contaminated agricultural products and tap water, and polluted the Pacific Ocean.

According to the latest official data, the March 11 earthquake and tsunami killed 11,232 people, while 16,361 people are missing, Japanese Kyodo news agency reported.

There are more than 175,000 people in the shelters currently, since whole cites in the northeast are devastated and turned into mud and rubble piles.

More than 70,000 people at the same time fled their homes, while another 130,000 are yet to be evacuated. According to official estimations, the disaster caused USD 300 billion damage.