South Korea’s top spy agency believes North Korea sent more than a million artillery shells to Russia since August to help fuel Russian President Vladimir Putin’s war on Ukraine, according to a lawmaker who attended a closed-door briefing Wednesday with intelligence officials.

North Korea and Russia have been actively boosting the visibility of their partnership in the face of separate, deepening confrontations with the US. Their diplomacy—highlighted by a summit between North Korean leader Kim Jong Un and Putin in September—has triggered concerns about an arms arrangement in which NKorea supplies Russia with badly needed munitions in exchange for advanced Russian technologies.