GREENPEACE says it has begun testing water samples from the ocean near Japan's crippled Fukushima Daiichi nuclear plant for radiation contamination.

The samples will be collected outside Japan's 12-mile territorial waters in line with government rules, Greenpeace said, adding that it would continue to press Tokyo for permission to study water within 12 miles of shore.

The plant has leaked radiation into air, soil and ocean since it was severely damaged by the massive March 11 quake and tsunami, and government readings at the end of March found levels of radioactive iodine-131 3,355 times the legal limit in nearby sea.

Greenpeace has stressed the importance of an independent study of the level of contamination.

Local fishermen have already been ordered to stop catching certain kinds of fish, especially konago or sand lance, which have shown high levels of radioactivity.

Originally published as Greenpeace testing water near reactor