Foreign Minister Taro Kono summoned the top South Korean envoy in Tokyo on Friday to lodge a protest against Seoul's rejection of a proposal to set up a joint arbitration panel to settle the issue of wartime labor, a simmering problem that is weighing heavily on bilateral ties.
In his meeting with Ambassador Nam Gwan-pyo at the Foreign Ministry, Kono said Seoul's failure to address the issue violates international law.
The formal protest is likely to escalate the diplomatic tensions between the two countries, whose relations were already strained over new export regulations introduced by Japan on key materials that are used in chip and smartphone production.