China expressed outrage today at a proposal by a Japanese city to list letters written by World War II suicide pilots on a United Nations register -- alongside Anne Frank's diary.

Minami-Kyushu last week filed an application to include the Japanese kamikaze pilots' farewell letters on a Unesco world memory list, media including public broadcaster NHK have reported.

The museum wants to win registration in 2015, "to forever hand down the letters to generations to come as a treasure of human life", it says on its website.

Among documents on the Unesco register is the diary of Anne Frank, written by the Jewish girl who hid in Amsterdam with her family in an attempt to avoid Nazi deportation. She died at the Bergen-Belsen concentration camp in Germany in 1945.

"This is an effort to beautify Japan's history of militaristic aggression, and challenge the victory of the World Anti-Fascist War and the postwar international order," Chinese foreign ministry spokeswoman Hua Chunying said when asked about the letters.

Speaking at a regular press briefing, she added that Japan committed "numerous" crimes against humanity during World War II.

"This effort runs completely counter to UNESCO's objective of upholding world peace, and will inevitably meet strong condemnation and resolute opposition from the international community," she said.

Relations between Beijing and Tokyo are heavily coloured by history, particularly the rampage across China by Japan's imperial forces in the 1930s and 1940s, when Chinese government researchers say 20.6 million people were killed.