The U.S. says there will be a "firm response" as Ukrainian forces holding ground in Russia's Kursk region now face North Korean troops "engaging in combat."

South Korea's government said Thursday "effective and phased" measures will be taken over North Korea's dispatch of troops to fight for Russia against Ukraine, after the nation's spy agency confirmed that the North's soldiers have entered combat in Russia's Kursk.

South Korean and US intelligence services have confirmed the participation of North Korean soldiers in hostilities in Russia, particularly in Kursk Oblast. Source: ISW Details: South Korea's National Intelligence Service reported on 13 November that North Korean troops were participating in hostilities in Russia,