Japan's chief government spokesman says Tokyo is considering various moves including possible cutting funding for UNESCO after the United Nations body registered documents on the "Rape of Nanjing" in its Memory of the World.

Chief Cabinet Secretary Yoshihide Suga told reporters Tuesday that UNESCO's decision reflected only China's views over the 1937 assault on the Chinese city, when Japanese troops massacred between 40,000 and 300,000 Chinese civilians in what has become known as the Nanjing Massacre.

Suga questioned the decision's transparency and said Japan was considering various ways to protest, including "suspension of our contributions."

He said Japan would also seek UNESCO's organizational reform.

Chinese and Japanese estimates vary regarding how many died in the attack, viewed as one of the worst atrocities of the World War II era.