By Rocky Swift and Ju-min Park

TOKYO (Reuters) -Japan has protested a South Korean court order that assets seized from Mitsubishi Heavy Industries be sold off to pay compensation to two women subjected to forced labour for the company during Japan’s occupation of the Korean peninsula.

Support groups for South Korean forced labour victims praised the court’s “step forward” in granting compensation. However, high-ranking Japanese officials warned about serious implications to diplomatic relations already at risk.

Toshimitsu MOTegi, Japan’s foreign minister said Tuesday that Japan warned of serious consequences following the S.Korean forcible labour verdict issued by South Korea’s Daejeon District Court. This was in clear violation of international law.

Motegi, Japan’s foreign minister said that the court decision was “truly regrettable”, and warned against any serious impact on Japan-South Korea relations.

Motegi claimed that Japan called on the South Korean vice-consul to protest the verdict. Mitsubishi Heavy, however, stated it would appeal.

The bitter history of Japan’s occupation between 1910-1945 has hampered relations between these two important U.S. allies.

A dispute regarding export control has followed disagreements about recent rulings on wartime forced labor, such as in brothels.

Kim Sungjoo and Yang Geum-deok, both teens, were employed at a Mitsubishi plane factory in Nagoya.

In 2018, South Korea’s Supreme Court ordered Mitsubishi Heavy to pay compensation for the victims. However, the company did not comply with the order. Japan claimed that the case was resolved under the 1965 treaty.

Due to strong objections from Tokyo, a series of South Korean courts later allowed for the seizing of Mitsubishi Heavy assets.

A court official said that the Daejeon District Court of South Korea decided Monday that Mitsubishi Heavy must liquidate the trademarks and patents of the assets seized to provide compensation for the victims, both who are in their nineties.

Victims in Japanese Wartime Forced Labor supported group estimates that each female received compensation of around 210million won ($178,023).

A court official refused to verify the asset’s value.

While the issue of Japan’s next prime Minister has become a problem, candidates have shown little willingness to compromise to improve bilateral relations.