Vice Foreign Minister Park Yoon-joo lodged a formal complaint with acting ambassador Andrii Vieshkin and expressed "strong regret" that Zelensky had revealed the transfer at the UN General Assembly last Wednesday, Seoul confirmed on September 28.
President Lee Jae Myung called the disclosure "greatly disappointing" and said the transfer was a "highly sensitive issue" impacting national security.
The two soldiers, captured by Ukrainian forces in Russia's Kursk Oblast in early 2025, had told local media they wanted to be sent to South Korea. After more than a year of negotiations between Seoul and Kyiv, Zelensky announced the transfer, adding they had not been "easy to capture alive".
President Lee's office said in a statement that part of the reason for secrecy was to protect the North Korean soldiers' families, and noted that Kyiv also wanted the transfer kept secret to avoid criticism.
Ukraine's foreign ministry declined to comment when approached by the BBC.