North Korean soldiers deployed to the Kursk region of Russia have begun combat operations against Ukrainian troops, the U.S. State Department confirmed Tuesday.

Russia attacked the Ukrainian capital Kyiv with a sophisticated combination of missiles and drones for the first time in 73 days on Wednesday, authorities reported, as the Pentagon said most of the North Korean troops sent to help Moscow's war effort are fighting to drive Ukraine's army off Russian soil in the Kursk border

"Today I can confirm that over 10,000 (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,

"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.

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.

Former North Korean soldiers, operating under the name Defector Propaganda Corps, have provided Ukraine with materials aimed at encouraging North Korean military personnel serving in the Russian army to defect.

Former North Korean soldiers, operating under the name Defectors' Propaganda Corps, have delivered materials to Ukraine aimed at encouraging North Korean military personnel serving in the Russian army to desert.