BEIJING / NANJING - Nagoya Mayor Takashi Kawamura's refusal to take back his denial of the Nanjing Massacre has increased tension between the two cities, with the Chinese city declaring on Tuesday that it would suspend official contacts with its sister city in Japan.

Foreign Ministry spokesman Hong Lei expressed support for Nanjing's decision at a regular news conference on Wednesday.

"We have made our position clear on the Nagoya mayor's denial of the Nanjing Massacre and already lodged a solemn representation to the Japanese side," Hong said, adding that China is closely watching the issue.

As 2012 marks the 40th anniversary of the normalization of China-Japan diplomatic ties, Hong also asked the Japanese side to work on the improvement of bilateral relations in light of the principles enshrined in the four China-Japan political documents, as well as act in the interest of both peoples based on the spirit of learning from history.

Osamu Fujimura, Japan's chief cabinet secretary, said at a news conference on Wednesday that the Japanese government thinks "it isn't a issue for the state to interfere in" and the two cities should settle it by themselves.

Fujimura reaffirmed that Tokyo's view on the Nanjing Massacre "has not changed", saying: "It cannot be made impossible that the killing of noncombatants, looting and other acts occurred."

Following Kawamura's refusal to take back his previous statement, Hideaki Omura, governor of Aichi Prefecture, on Wednesday called on Kawamura to correct his comments on the Nanjing Massacre as soon as possible, warning that his remarks had created "a diplomatic issue".

Nagoya, the capital city of Aichi Prefecture in central Japan, established a sister-city relationship with Nanjing in December 1978.

Visitors on Wednesday pass a wall at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders, on which the number of victims, 300,000, is displayed. Yang Bo / Xinhua