Though North Korean ballistic missiles account for only a small portion of Russia's missile strikes they carry a large warhead of up to one tonne and have a range of up to 800 km, the military source said. The Iskander-M, an equivalent Russian missile, carries a smaller payload and has a shorter range of 500 km.

North Korean soldiers previously fighting alongside Russia's army on the Kursk front line appear not to have been engaged in combat since mid-January, South Korea's spy agency told AFP on Tuesday, after Ukraine claimed they had been withdrawn following heavy losses.

A Ukrainian news outlet has published a video showing the capture of a North Korean soldier, as South Korea's spy agency said Kim Jong Un has pulled troops from Russia's Kursk region. Newsweek has contacted the Russia's Foreign Ministry for comment.

One Ukrainian special forces soldier shares details of how his team captured the North Korean, giving an insight into the North Korean mindset.

We still don’t know for sure if there are North Korean troops fighting in Russia against Ukrainian forces. Perhaps we never will. But Ukraine’s case for their presence was not made stronger by the sudden announcement on January 30 that they were gone.