South Korean President Lee Jae Myung has warned of unspecified "further action" if Ukraine does not publicly apologise for revealing that two North Korean prisoners of war had been transferred to the South. The dispute began last week, when Ukrainian President Volodymyr Zelensky disclosed the transfer in an address to the UN General Assembly in New York.

Seoul says the matter was meant to remain confidential. A senior South Korean foreign ministry official said on Friday that there had been an agreement from the outset to keep the transfer secret, to protect the soldiers and their families, who remain in North Korea. Lee's office has said Ukraine itself asked for secrecy, partly for that reason and partly because Kyiv wanted to avoid criticism that it had passed up a chance to exchange the soldiers for Ukrainian prisoners. Zelensky's office has said no such agreement existed. Lee has said the denial made him look like a "liar" and has described the matter as one concerning "the dignity of the Korean people and the nation".

The two soldiers were captured in January 2025 while fighting for Russia in the Kursk region and arrived in South Korea in mid-September, according to officials. They were among thousands of North Koreans sent to support Russia in the war, and had told local media they wanted to go to South Korea.

Ukrainian Foreign Minister Andrii Sybiha tried to calm tensions on Thursday, calling the affair a "diplomatic misunderstanding" and saying Kyiv was working to resolve it. "South Korea is an important country for us," he said. Lee rejected that framing. He also took issue with Ukrainian talk of an "imminent military clash" between the two Koreas, apparently referring to remarks by Kyrylo Budanov, head of Ukraine's presidential office, who said North Korea was learning from the war in Ukraine to prepare for combat in its own region. Lee said such statements appeared to hope for war on the Korean Peninsula.

Despite the sharp public exchange, diplomacy continues. The South Korean official said Foreign Minister Cho Hyun and Sybiha have been in close contact on the tone, content and manner of announcement of a possible Ukrainian response, which would take into account Ukraine's war with Russia. Seoul, he said, also wants to build a good relationship with Ukraine and avoid broader friction.

The row matters for domestic and international reasons. Lee has faced heavy criticism at home, with the opposition accusing him of covering up the transfer to appease Pyongyang. Internationally, the dispute pits two US-aligned states against each other and could complicate efforts to maintain a united front against Russia, China and North Korea. Seoul has been sympathetic to Ukraine since Russia's full-scale invasion but has kept to its long-standing policy of not supplying lethal weapons to countries in active war.