Chinese authorities in Nanjing have suspended official contacts with Nagoya following the Japanese city's mayor's denial of the well-documented massacre of Chinese civilians by Japanese troops in 1937.
300,000 people were killed that year in an orgy of murder, rape and destruction when the eastern city of Nanjing -- then the capital -- fell to the Japanese army, and the incident has haunted Sino-Japanese ties ever since.
According to Japan's Kyodo news agency, Takashi Kawamura, mayor of Nagoya, told Liu Zhiwei, a high-level Chinese official visiting from Nanjing, that he believes only "conventional acts of combat" took place.
During talks on Monday between the two -- whose cities were twinned in 1978 -- Kawamura, whose father was in Nanjing in 1945 at the end of the Japanese occupation of China, reportedly denied that mass murders and rapes happened.
Some Japanese academics also contest the number of casualties in Nanjing, and say estimates range from 20,000 to 200,000.
Kawamura's comments have triggered outrage in China and the Nanjing municipal party committee announced late Tuesday it had suspended ties with Nagoya.
"In view of the current denial by Nagoya mayor Takashi Kawamura of historical facts pertaining to the Nanjing Massacre, which seriously hurt Nanjing people's feelings, Nanjing city is suspending official contact with the government of Nagoya," it said on its official Twitter-like weibo account.
China's foreign ministry spokesman Hong Lei on Monday also waded into the controversy, hitting back at Kawamura's comments.
"The Nanjing Massacre was a brutal crime committed by Japanese military during their war and invasion, and there is irrefutable evidence," he said.
"Some Japanese people should correctly understand... that period of history, and earnestly draw lessons from history."