TOKYO - Japan’s Foreign Ministry summoned a senior diplomat from the South Korean embassy in Tokyo to protest a Supreme Court ruling that Japanese companies should pay compensation to Koreans conscripted to work for the firms during colonial occupation. 

Mr Hiroyuki Namazu, director-general for Asian and Oceanian Affairs, told the official on Dec 28 that the South Korean court’s ruling against Mitsubishi Heavy Industries and Hitachi Zosen was a violation of a 1965 treaty and unacceptable, the ministry said in an e-mail. 

The protest comes amid a historic warming of often fraught ties between the two US allies under conservative South Korean President Yoon Suk-yeol.

Mr Yoon took part in an unprecedented trilateral summit with Japanese Prime Minister Fumio Kishida and President Joe Biden in the US in August.

The neighbours have frequently been at odds over whether Japan has sufficiently compensated South Korea for its 1910 to 1945 colonial occupation of the Korean peninsula.

Concern that Japanese corporate assets could be sold off to pay compensation contributed to a downturn in relations in 2019 that damaged trade ties and threatened military cooperation.

During World War II, hundreds of thousands of Korean men were sent to Japan to work, often in brutal conditions, in factories and mines that supplied the imperial war machine.

Japan says all claims over the practice were settled by a 1965 treaty, which was accompanied by about US$800 million (S$1.05 billion) in aid. 

South Korean court rulings since late 2018 have said some conscripted workers were not properly compensated for their emotional suffering. 

Any compensation in such cases should be paid by a fund established by South Korea, as proposed in March 2023, Mr Namazu told the South Korean diplomat.

No payments have been made by any of the Japanese companies subject to lawsuits in South Korea, with the process slowed by judicial procedural complications that could take years to unwind. BLOOMBERG