South Korea’s President Lee Jae Myung threatened to take unspecified further action if Ukraine does not issue a public apology for revealing that two North Korean prisoners of war had been sent to the South, according to the BBC.

The South Korean president expressed anger at Ukraine over comments by Ukrainian President Volodymyr Zelenskyy in a speech at the UN that appeared to reveal a secret deal, according to Al Jazeera. Ukraine’s Foreign Minister Andrii Sybiha described the situation as a “diplomatic misunderstanding” and said Kyiv was working to resolve it, according to the BBC.