South Korea’s foreign ministry summoned Ukraine’s acting ambassador on Monday to protest against Kyiv’s disclosure of the transfer of captured North Korean soldiers to South Korea, and demanded an official explanation and apology.

The ministry said it had called in acting ambassador Andrii Vieshkin and expressed strong regret that Ukrainian President Volodymyr Zelenskiy made the disclosure at the United Nations General Assembly, despite what Seoul said was a clear agreement between the two countries to keep the matter confidential.

South Korea also protested against what it called a false statement by the Ukrainian presidential office denying that such a confidentiality agreement existed, and urged Kyiv to take steps to prevent a recurrence, the ministry said in a statement.

“First Vice Minister Park Yoon-joo stressed that the disclosure of a falsehood that there was no confidential agreement seriously undermines trust between the two governments and is an action that can cause problems for friendly ties,” it said.

South Korean media have reported that Kyiv has said there was an understanding of the plan to make the transfer public.

Vieshkin said he had listened carefully to Seoul’s position and would accurately report it to his government, the media reports added.

Zelenskiy told the UN General Assembly last week that Ukraine had transferred two captured North Korean soldiers to South Korea. He said the men had recently been sent there after being captured while fighting for Russia in its war against Ukraine. Ukrainian authorities were not immediately available for comment.

South Korea’s presidential office on Sunday had also demanded an official explanation and apology from Ukraine.

The transfer comes as South Korea has backed efforts to revive dialogue with North Korea and US President Donald Trump has renewed his willingness to engage with Pyongyang.