Greenpeace said its teams collected samples of marine life along the Fukushima coast and in international waters outside Japan's 12-mile territorial limit. The samples were tested by nuclear research laboratories in France and Belgium, and high levels of radioactive iodine and cesium were found, it said.
Fish, shellfish and seaweed all showed significant levels of radioactive contamination, according to Greenpeace. All are widely consumed in Japan.
Besides consumers, fishermen are at risk from the elevated radiation levels, Greenpeace said.