Documents related to the Nanjing Massacre are being submitted for inclusion on a UNESCO list by authorities in the Chinese city, state media reported Thursday, after uproar over a Japanese bid to include suicide pilots' farewell letters.

According to the Shanghai-based Oriental Morning Post, it is the third time that Nanjing has submitted the documents for inclusion in UNESCO's Memory of the World Register, which also includes such items as the diary of Anne Frank and Britain's Magna Carta.

The cache includes documents related to the atrocities committed by Japanese soldiers in the eastern Chinese city, where Tokyo's imperial forces went on a six-week spree of rape, slaughter and destruction from December 1937. Estimates of the dead range as high as 300,000 people, although some are much lower.

The papers also include files on the use of "comfort women" forced into sex slavery by Japanese troops, the newspaper said.

Relations between Beijing and Tokyo are heavily coloured by their shared history, and tensions have escalated amid a row over disputed islands controlled by Japan but claimed by China.

A senior manager at Japanese national broadcaster NHK, Naoki Hyakuta, drew fire earlier this month when he denied that the Nanjing massacre had ever taken place.

"Countries in the world ignored the propaganda produced (by then-Chinese leader Chiang Kai-shek)... that Japan's troops carried out a massacre in Nanjing. Why? There was no such thing," Hyakuta said, according to the Japanese daily Asahi Shimbun.

Another NHK official said last month that the practice of forcibly drafting women into military brothels during World War II was "common in any country at war".

The Japanese city of Minami-Kyushu drew widespread condemnation last week when it made a bid for the inclusion of letters written by World War II kamikaze pilots on the UNESCO register.

The Chiran Peace Museum -- named after the small Japanese town from which kamikaze planes would depart on their flight of no return -- is seeking the documents' inclusion "to forever hand down the letters to generations to come as a treasure of human life", it says on its website.

Both Beijing and Seoul swiftly blasted the move, which Chinese foreign ministry spokeswoman Hua Chunying contended was "an effort to beautify Japan's history of militaristic aggression".