SEOUL: A South Korean court on Wednesday dismissed a case brought by a handful of World War II sex slaves and their families against the Japanese government, citing Tokyo's "sovereign immunity", reports said.

The ruling comes after the same court in January ordered Tokyo to pay compensation to a handful of women forced to serve Japanese troops -- euphemistically labelled "comfort women" -- marking the first civilian legal victory against Tokyo in the South.

But the Seoul Central District Court dismissed a separate case on Wednesday after "reaching the decision that sovereign immunity must be applied to the Japanese government", Yonhap news agency reported.

The comfort women issue has been at the core of frosty ties between the two neighbours, despite a 1965 treaty between Seoul and Tokyo which declared claims between them and their nationals had been settled.

Tokyo and Seoul are both major US allies, democracies and market economies, but their rift -- which has worsened significantly in recent years -- presents US president Joe Biden with an immediate foreign policy headache as he seeks to build a common front on China and nuclear-armed North Korea.

Biden held his first summit with Japanese Prime Minister Yoshihide Suga at the weekend and will meet with South Korean President Moon Jae-in next month.

Mainstream historians say up to 200,000 women, mostly from Korea but also other parts of Asia including China, were forced to work in Japanese military brothels during World War II.

The Japanese government denies it is directly responsible for the wartime abuses, maintaining that the victims were recruited by civilians and that the military brothels were commercially operated.