North Korean state media on Tuesday released images of leader Kim Jong Un mourning over flag-draped coffins of North Korean soldiers killed while fighting alongside Russian forces in Ukraine, as South Korea’s Defense Ministry said it has yet to see signs of additional troop deployments from the North.

The nuclear-armed North has emerged as one of Russia’s key allies since the full-scale invasion of Ukraine, sending thousands of troops and shipments of weapons to bolster the Kremlin’s efforts to drive Ukrainian forces from the Kursk border region.

Around 600 North Korean soldiers have been killed and thousands more wounded while fighting for Russia, according to South Korean lawmaker Lee Seong-kweun, who cited intelligence from Seoul’s spy agency.

Footage aired by Korean Central Television showed a solemn Kim placing a North Korean flag on a coffin during a ceremony in Pyongyang on Sunday. The event — attended by Russian Culture Minister Olga Lyubimova — marked the one-year anniversary of a military pact between Pyongyang and Moscow that includes a mutual defense clause.