South Korea’s foreign ministry summoned Ukraine’s acting ambassador on September 28 to protest the disclosure of a confidential prisoner deal and demand an official explanation and apology. The move signals rare friction between two governments cooperating against Russia’s invasion of Ukraine.

President Volodymyr Zelenskiy told the UN General Assembly that Ukraine had transferred two captured North Korean soldiers to South Korea. Seoul says the two sides had agreed to keep the transfer confidential. It also protested what it called a false statement from Ukraine’s presidential office denying that any confidentiality agreement existed.

South Korea said it agreed to secrecy for security, diplomatic and humanitarian reasons, including the safety of the prisoners and their families. Officials warned that the disclosure seriously undermines trust between the two governments and could harm bilateral relations.

The incident comes as Seoul navigates a delicate position on the war. South Korea has backed Ukraine diplomatically while weighing the risk of North Korea deepening its military cooperation with Moscow, including the deployment of troops to fight alongside Russian forces.