South Korea's foreign ministry said Tuesday that Seoul and Kyiv had a "clear understanding" to keep confidential the transfer of two North Korean prisoners of war, captured in Russia's Kursk region in January 2025, after Ukrainian President Volodymyr Zelenskyy revealed it in a UN General Assembly speech and Ukraine later denied any such agreement. Seoul has demanded an official apology and explanation and summoned Ukraine's acting ambassador, saying the disclosure could endanger the soldiers and their families and affect security on the Korean Peninsula. The ministry said the matter is a humanitarian issue and will not affect South Korea's aid to Ukraine or reconstruction cooperation.