South Korea’s spy agency said it is in the process of verifying intelligence about the U.S. government’s announcement that there have been casualties among North Korean troops sent to fight in the Russia-Ukraine war.

At a press briefing on Monday, Pentagon Press Secretary Maj. Gen. Pat Ryder said Washington believes North Korean soldiers have engaged in combat in Kursk alongside Russian forces.

The spokesperson said there are indications that some of the North Korean soldiers have been killed and others wounded, but he did not state a specific number of casualties.

Ryder said the North Korean forces are legitimate military targets for the Ukrainians, given that they are engaged in active combat operations.

This is the first time the U.S. government has confirmed combat engagement by North Korean troops and the emergence of casualties.

Amid foreign media reports about North Korean casualties in the Russia-Ukraine war last month, Seoul’s National Intelligence Service said it was closely verifying related intelligence.