"Over 10,000 DPRK (North Korean) soldiers have been sent to eastern Russia, and most of them have moved to the far western Kursk Oblast, where they have begun engaging in combat operations with Russian forces," State Department spokesperson Vedant Patel told reporters at a briefing.

North Korean soldiers have begun fighting against Ukraine alongside their Russian allies, the US State Department said, after Pyongyang sent thousands of troops to Russia’s Kursk region to aid the Kremlin’s war efforts.

Nearly all would raise their hands to go, ex-military defectors explain, owing to regime loyalty, promise of higher status and a glimpse of the outside world.

Ukrainian officials expect a counteroffensive in western Russia to begin in the coming days as North Korea’s troops train with Russian forces.

Ukraine's military intelligence has intercepted what it claims are radio communications between North Korean soldiers in Russia, amid media reports of a massive troop buildup ahead of an attack in the Kursk region.

The presence of North Korean soldiers alongside Russians fighting Ukraine raises many tactical and military questions, leading some analysts to wonder about their effectiveness and ultimate objectives.