He also warned of negative security impacts for Asia as Russia is teaching North Korean troops the methods of modern warfare, including drone use.Separately, a Ukrainian military intelligence spokesperson told the media that 2,000 North Korean troops have been assigned to Russia's Marine and airborne units fighting on the front."If they (North Korean troops) have joined units engaged in active hostilities, then we can confidently say that they have joined the fight," spokesperson Andrii Cherniak told Radio Free Europe/Radio Liberty, adding that this might not necessarily mean deployment on front-line positions."Maybe they are not in advanced positions, but they enable aggression against Ukraine, ensure the killing of Ukrainian service members."North Korea is Russia's leading ally in its war against Ukraine, reportedly providing Moscow with over 100 ballistic missiles and 5 million artillery shells.