South Korea said Thursday it will recall its ambassador to Ukraine, escalating its protest over Ukrainian President Volodymyr Zelenskyy's disclosure of an alleged secret transfer of two North Korean prisoners of war to South Korea.

The announcement came days after South Korean President Lee Jae Myung warned that Seoul could take unspecified punitive measures if Ukraine does not apologize for revealing the transfer.

South Korea's Foreign Ministry did not say when Ambassador Park Hee-chang would return home. In a statement, the ministry said Seoul would continue discussions with Kyiv and expressed hope that the dispute could be resolved smoothly.

The diplomatic dispute began after Zelenskyy mentioned the transfer of the two North Korean soldiers during his speech at the United Nations on Sept. 23.

South Korea has accused Ukraine of violating a nondisclosure agreement covering the soldiers' transfer in mid-September. Kyiv has denied that such an agreement existed.

The two soldiers were among thousands of North Korean troops sent to support Russia's war against Ukraine. After being captured in early 2025, they said they wanted to settle in South Korea because they could face persecution if returned to North Korea.

South Korea had agreed to accept them because it legally considers North Korea part of its territory and has a policy of receiving and providing financial support to North Korean defectors.

South Korean officials said the nondisclosure arrangement was intended to protect the soldiers and their relatives in North Korea. However, some experts believe South Korea's liberal government may also be concerned that publicizing the soldiers' arrival could complicate its efforts to improve relations with Pyongyang.

North Korean state media has not commented on the transfer. However, Pyongyang has previously reacted angrily to major defections, accusing Seoul of abducting North Korean citizens.

North Korea has avoided talks with South Korea and the United States since 2019 while focusing on expanding its nuclear weapons program.

It remains unclear what further measures Seoul may take against Ukraine. Experts say maintaining relations with Kyiv is important for South Korea because Ukraine could provide intelligence on North Korea's growing military cooperation with Russia and the battlefield experience of North Korean troops.

They also said cooperation with Ukraine is important for South Korea's ties with Western countries supporting Kyiv in the war.

Observers believe Zelenskyy disclosed the transfer to highlight the risks posed by North Korea's military support for Russia and encourage greater international assistance for Ukraine.

South Korea has provided $445 million in humanitarian aid to Ukraine since 2022. In July, Lee pledged another $100 million in aid to Ukraine during a meeting with Zelenskyy.