Ukrainian forces have captured an injured North Korean soldier who was sent to support Russia's war, South Korea's spy agency confirmed Friday.

The soldier is believed to be the first North Korean prisoner of war captured since December, when Pyongyang deployed forces to support Russia's war in Ukraine.

The confirmation comes after a photo purporting to show the wounded soldier circulated on Telegram.

North Korea has sent more than 10,000 soldiers to help Russia, according to Kyiv and Seoul - though Moscow and Pyongyang have neither confirmed nor denied their presence.

Over 3,000 North Korean troops have died or been wounded while fighting in Kursk, Ukrainian President Volodymyr Zelenskyy said Monday.

He added that the collaboration between Moscow and Pyongyang heightens the "risk of destabilisation" around the Korean peninsula.