Police arrested on Saturday a 42-year-old man on suspicion of mailing radioactive materials to 10 government offices last week with a message claiming nuclear materials were being smuggled to North Korea.

Police arrested Tsugio Uchinishi, of Tokyo's Nakano Ward, and searched eight locations, including his residence, police officials said.

Uchinishi has admitted mailing the substance, monazite powder, and was quoted by police as saying he wanted to draw attention to his claim that a broker, an acquaintance of the director of a foundation supervised by the Education Ministry, is illegally exporting nuclear materials to North Korea.