The intelligence report comes days after Ukraine's president said nearly 3,000 North Korean soldiers had been 'killed or wounded' in the war.
A North Korean soldier, who fought for Russia, has died while in captivity in Ukraine due to severe wounds, according to a spyware organization in South Korea.
The announcement by the National Intelligence Service in Seoul came on Friday, hours after the Yonhap news agency reported that the agency was confirming for the first time that Ukrainian forces had captured a North Korean soldier. The report said he was alive, although where he was captured is not known.
Pyongyang has sent thousands of soldiers strengthening Russian forces, especially in the Kursk border region where Ukraine advanced in August.
Confirmation of the soldier's death came a few days later from the President of Ukraine Volodymyr Zelenskyy he said about 3,000 North Korean soldiers were “killed or wounded” as they joined Russian forces in the battle.
It was Ukraine's first significant estimate of North Korean casualties weeks after Kyiv announced that North Korea had sent 10,000 to 12,000 troops to Russia to help in the three-year war.
Ukrainian military officials, known as GUR, say North Koreans have suffered heavy casualties as a result of Ukrainian strikes near Novoivanovka in Kursk, supplies and lack of drinking water.
Strong relationships
North Korea and Russia have strengthened their military ties since Moscow annexed Ukraine in February 2022.
A defense pact between Pyongyang and Moscow signed in June came into effect this month, with Russian President Vladimir Putin calling it a “successful document”.
Ukrainian allies said that Pyongyang's escalation of Russia's war in Ukraine is a “dangerous escalation” of the war.
South Korean politician Lee Seong-kweun said last week that Pyongyang's military was “being used as frontline combat units”.