An extraordinary diplomatic row has erupted between South Korea and Ukraine as Seoul accused Kyiv of violating a secrecy agreement over the fate of captured North Korean soldiers. The dispute was sparked by Ukraine’s President Volodymyr Zelenskyy’s speech at the UN General Assembly in New York last week, when he revealed that two North Korean soldiers captured in Russia had been sent to South Korea.

South Korea’s senior presidential secretary Sung Ki-hong late on Sunday evening expressed “strong regret” over Ukraine’s decision to “unilaterally and abruptly” make the transfer public. He said Ukraine had requested the transfer be kept confidential, to which Seoul had agreed because of the sensitivity of the matter. “We demand an official explanation and an apology,” he added.

Dmytro Lytvyn, Zelenskyy’s communications adviser, denied South Korea’s accusations, writing on Facebook that “there was no such agreement”. The incident has driven a wedge between South Korea and Ukraine despite their shared interest in countering North Korea’s military partnership with Russia. Kyiv has sought arms from South Korea but Seoul has refused, citing its policy of only providing humanitarian aid to active war zones.

Senior officials in Kyiv have also expressed deep frustration with what they see as Seoul’s deepening business ties with Moscow, pointing to the transfer of 30,000 metric tonnes of refined fuels to Russia in July.