North Korean soldiers sent to fight in Russia's Kursk region haven't been seen for several weeks, reports say.

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engaged in combat since mid-January, South Korea's spy agency told AFP on Tuesday, after Ukraine claimed they had been withdrawn following heavy losses.

North Korean troops, largely special ops forces, have suffered high casualties in bloody assaults not unlike other units, including prison units.

It also shed some light on the mindset and training of the conscripted North Korean soldiers sent to fight Russia’s war a continent away from their home. Highly disciplined, ready to die but also very young and with little battlefield experience they elicited curiosity and even some pity from the Ukrainian soldiers who captured them during two separate missions on Jan.

A North Korean soldier captured fighting for Russia in Ukraine last month reportedly made just two requests to his captors - one for water and another for a cigarette

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