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.

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."

Ukraine’s allies will look to pressure China over North Korea’s growing support for Russia’s war during a Group of 20 Summit in Brazil, according to people familiar with the matter.