A new Asian diplomatic row broke out Monday after China unveiled a memorial to a Korean national hero who assassinated a Japanese official a century ago -- with Tokyo condemning him as a "terrorist".

In 1909, Ahn Jung-Geun shot and killed Hirobumi Ito, Japan's first prime minister and its top official in Japanese-occupied Korea, at the railway station in the northeast Chinese city of Harbin.

Ahn was hanged by Japanese forces the following year, when Korea also formally became a Japanese colony, heralding a brutal occupation that lasted until the end of World War II in 1945.

A joint Chinese-South Korean memorial hall in Ahn's honour was unveiled at the train station on Sunday.

Yoshihide Suga, Japan's top government spokesman, said Monday that Tokyo had conveyed its regret to Beijing and Seoul over the monument.

"We recognise Ahn Jung-Geun as a terrorist who was sentenced to death for killing our country's first prime minister," Suga said.

"I cannot help saying that it is not contributing to building peace and cooperative relations in this region that South Korea and China took the joint cross-border move based on unilateral evaluation on a matter that happened in the previous century," he added.

Political relations between China, Japan and South Korea -- Asia's first, second and fourth-largest economies -- are heavily coloured by 20th-century history, when Tokyo's imperial forces rampaged across the region.

Beijing and Tokyo are embroiled in a bitter row over disputed islands in the East China Sea, and tensions rose further last month when Japanese Prime Minister Shinzo Abe visited a controversial shrine that honours Japan's war dead, including indicted war criminals.

In an echo of Abe's comments after his appearance at the Yasukuni shrine, Chinese and South Korean officials hailed the memorial to Ahn and contended that it was intended not to provoke a diplomatic row, but rather to promote peace.

"People have cherished the memory of Ahn for the past century," Sun Yao, the vice governor of China's Heilongjiang province, said at the unveiling, according to China's official Xinhua news agency.

"Today we erect a memorial to him and call on peace-loving people around the world to unite, resist invasions and oppose war."

South Korea's foreign ministry on Monday welcomed the opening, adding that Ahn was "a widely respected figure in both South Korea and China" and describing the assassination as a "courageous act".

"We hope that the museum will offer an opportunity for northeast Asian countries to... set the path for genuine peace and cooperation based on correct historical awareness," it said.

Ahn was posthumously awarded the Order of Merit for National Foundation in 1962, South Korea's most prestigious civil decoration, for his efforts for Korean independence.

Every schoolchild learns his story from an early age -- he has been the subject of movies, books, even musicals, and there are numerous statues and memorials to him across the country.

Bitter legacy

Japan's occupation has left a bitter legacy in China and both Koreas, and Ahn remains a potent symbol -- in July fans at an East Asia Cup football match between South Korea and Japan in Seoul unveiled a giant banner of his image.

Abe was the first sitting Japanese prime minister since 2006 to visit the controversial Yasukuni shrine, which honours several high-level officials executed for war crimes after World War II and serves as a reminder of Japan's 20th century aggression.

Abe insisted that he had "no intention at all to hurt the feelings of Chinese or South Korean people" and that the aim of his visit was "to pledge to create an era where people will never suffer from catastrophe in war".

China has responded with a global public relations offensive against Abe, who was elected just over a year ago, with ambassadors in more than 30 countries penning articles condemning the move.

In a commentary Sunday, Xinhua wrote that "the opening of Ahn's memorial is not to inflict pain, but to shed light on the history of northeastern Asia".

"History is the teacher of life," the commentary continued. "Alarm bells shall not go unheeded. With Japan treading a dangerous path once again, the need for vigilance and a joint international effort is clear if we are to prevent a Japanese militarist resurgence."