South Korea’s spy agency says North Korea appears to have sent additional troops to Russia, after its soldiers deployed on the Russian-Ukraine fronts suffered heavy casualties.

Ukrainian troops holding positions in Kursk say the North Koreans have reappeared on the battlefield and become even more formidable foes.

North Korea has sent more soldiers to Russia and re-deployed several to the frontline in Kursk, Seoul's spy agency told AFP on Thursday. However, an official from Seoul's National Intelligence Agency said on Thursday they had been "redeployed" there.