TOKYO - Japan's foreign ministry claims to have found an atlas published by the Chinese government in 1969 which identifies disputed islands in the South China Sea by their Japanese name Senkaku Islands.
The ministry posted the maps on its website on Monday, local media reported.
Friction between the two countries has existed for long over a chain of uninhabited islets, known in China as Diaoyu and in Japan as Senkaku.
The existence of the Chinese map was revealed last month at a Lower House committee session by a ruling Liberal Democratic Party lawmaker.
Foreign Minister Fumio Kishida evaluated the map as precious, and said the ministry had been considering making it public.
"This is valuable data. By utilising various data, we must continue to strategically send our message abroad," Mr Kishida said, according to Yomiuri Shimbun.
The Foreign ministry said the map with references to Senkaku is part of an atlas published in 1969 by the then Chinese State Bureau of Surveying and Mapping. In addition to referring the overall group of islands as the "Senkaku Islands" in Japanese characters, the name of Uotsuri Island, the westernmost island in the group, is also written in Japanese characters, the ministry said.
"China had changed its name for the islands since it started claiming sovereignty over them. This indicates that China regarded the islands as belonging to Japan back then, and will serve as corroborating evidence to Japan's assertions," the Shimbun newspaper quoted a senior foreign ministry official as saying.