The U.S. State Department has confirmed that North Korean troops deployed to Russia’s Kursk region are engaging in combat against Ukraine.

In a press briefing Tuesday, State Department spokesperson Vedant Patel said he can confirm that over ten-thousand North Korean soldiers have been sent to eastern Russia, and that most have moved to the far western Kursk Oblast, where they are fighting alongside Russian forces. 

Patel added that Russian forces have been training North Korean troops in artillery, unmanned aerial vehicle and basic infantry operations, including trench-clearing operations, which he said are “critical” skills for front-line operations.

The spokesperson continued that Russia’s battlefield success using North Korean troops will in large part be dictated by how well Russia can integrate them into its military.

Patel said Russia needs to overcome challenges regarding interoperability, the language barrier, command and control, and communications.

He added that the United States is consulting closely with its allies and partners in other countries in the region on the implications of these developments.