China and South Korea are to cooperate on a memorial to a Korean national hero who assassinated a Japanese official a century ago, provoking a diplomatic row Tuesday.
Relationships between all three neighbours are heavily coloured by history, while both Beijing and Seoul are embroiled in separate territorial rows with Tokyo over disputed islands.
The latest flashpoint between them is Ahn Jung-Geun, who shot and killed Hirobumi Ito, then Japan's top official in Korea, at the railway station in Harbin in northeast China in 1909.
Ahn, a Korean nationalist, killed Ito in response to Japan's colonial designs over the Korean peninsula where its influence had been growing.
He was hanged the following year, when Korea also became a formal Japanese colony, heralding a brutal occupation which lasted until the end of World War II in 1945.
Japan already held territory in mainland China at the time and went on to invade Manchuria in the 1930s before occupying most of eastern China during the war.
South Korean President Park Geun-Hye met China's top foreign policy official Yang Jiechi on Monday. Both said work was progressing on a monument in Harbin to Ahn, according to a statement by the presidential Blue House in Seoul.
"Ahn Jung-Geun is a very famous anti-Japanese fighter in history," Beijing's foreign ministry spokesman Hong Lei said at a regular briefing Tuesday. "He is respected by the Chinese people as well."
"China will in accordance with relevant regulations on memorial facilities involving foreigners make a study to push forward relevant work."
Ito, Japan's first prime minister, was one of the most significant figures in the country's modern politics and Tokyo vehemently opposes the monument.
"We have been telling the South Korean government that Ahn Jung-Geun was a criminal," Chief Cabinet Secretary Yoshihide Suga, the government's top spokesman, told reporters on Tuesday.
"I'm afraid this is not good for relations between Japan and South Korea."
South Korean Foreign Ministry spokesman Cho Tai-Young fired back with a defence of Ahn, who is also a hero in North Korea.
"Martyr Ahn sacrificed his life not for the country's independence but regional peace as well," Cho said.
"It is highly regretful to call such a person a criminal. We again strongly urge Japan to face truth in history and repent on its past wrongs."
Japan's occupation has left a bitter legacy in China and both Koreas. Seoul and Beijing have refused to hold formal bilateral summits with Japanese Prime Minister Shinzo Abe, seen by both countries as hawkish on the issues of territory and history.