TOKYO (Reuters) - Japan protested to China on Wednesday after Beijing applied for the inclusion of the 1937 Nanjing massacre and the “comfort women” forced to work in wartime military brothels in a UNESCO program, the latest flare-up of tensions in relations.

A man stands as pigeons fly during a ceremony marking the 75th anniversary of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province, December 13, 2012. REUTERS/Carlos Barria

Ties between China and Japan, the world’s second- and third-largest economies, have been strained by a territorial row over a group of East China Sea islets and Chinese allegations that Japan has not properly atoned for wartime aggression.

“It is extremely regrettable that China is trying to play up a negative legacy from a certain period in Sino-Japanese history by using UNESCO for a political purpose, when effort needs to be made to improve ties between Japan and China,” Chief Cabinet Secretary Yoshihide Suga told a regular news conference.

“Today, we made a protest, and asked China for a withdrawal.”

China’s foreign ministry said on Tuesday that Beijing had submitted an application to UNESCO to include the issues of the “comfort women”, many from Korea and China, who were forced to work in Japanese military brothels, as well as the 1937 mass killings in Nanjing.

Beijing said the submissions were part of a need to “remember history, cherish peace and avert similar atrocities from happening again”.

UNESCO’s Memory of the World program, launched in the 1990s, has registered dozens of projects to reflect the “documentary heritage” of different periods. Documents include Britain’s 13th century Magna Carta, the World War Two Diary of Anne Frank and an annotated copy of Karl Marx’s Das Kapital.

China consistently reminds its people of the 1937 Nanjing Massacre in which it says Japanese troops killed 300,000 people in the then-national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place.

Both China and South Korea have long sought compensation for women victimized in the wartime brothels. In a landmark 1993 statement, then-Chief Cabinet Secretary Yohei Kono recognized the involvement of Japanese authorities in coercing the women, although many conservative Japanese say there is no proof of direct government involvement.

In February, China condemned an application by a Japanese city to ask UNESCO to register in the same program the wills and farewell letters of World War Two kamikaze suicide pilots to highlight the importance of world peace.