Japanese scientist Masatoshi Koshiba, a co-winner of the 2002 Nobel Prize in physics, holds his medal in Stockholm in December 2002. (Kyodo)

TOKYO - Japanese scientist Masatoshi Koshiba, a co-winner of the 2002 Nobel Prize in physics for his pioneering contribution in the field of astrophysics, has died, the University of Tokyo said Friday. He was 94.