Ukraine captured two wounded North Korean soldiers who were fighting on behalf of Russia in a Russian border region, South Korea’s intelligence service said, confirming an account from Ukrainian President Volodymyr Zelenskyy on Saturday.

Seoul’s National Intelligence Service (NIS) told AFP it has “confirmed that the Ukrainian military captured two North Korean soldiers on January 9 in the Kursk battlefield in Russia.”

The confirmation comes after Zelenskyy said in a post on the Telegram messaging app that the two captured North Korean soldiers were wounded and taken to Kyiv, where they are communicating with Ukrainian security services SBU.

SBU released video that appears to show the two prisoners on beds inside jail cells. The authenticity of the video could not be independently verified.

While reports of their presence first emerged in October, Ukrainian troops only confirmed engagement on the ground in December.

On Thursday, Zelenskyy put the number of killed or wounded North Koreans at 4,000, though U.S. estimates are lower, at around 1,200.

Soldiers are seen at Kim Il Sung Square in Pyongyang, North Korea, on Oct. 12, 2020.  (AP Photo/Jon Chol Jin, File)

Despite North Korea’s suffering losses and initial inexperience on the battlefield, Ukrainian soldiers, military intelligence and experts suggest first-hand experience will only help them develop further as a fighting force.

“For the first time in decades, the North Korean army is gaining real military experience,” Yusov said. “This is a global challenge — not just for Ukraine and Europe, but for the entire world.”

The Associated Press contributed to this report.