As of now, there is no verified or credible news confirming that North Korea has officially declared war on Ukraine or that North Korean troops are actively fighting in Kursk.

What you shared sounds very suspicious — it might be misinformation or a viral rumor.

Here are key points:

North Korea has politically supported Russia in the Ukraine conflict but has not officially declared war on Ukraine.

There have been rumors about North Korea supplying weapons (like artillery shells) to Russia, but no official deployment of soldiers has been confirmed by trusted sources like Reuters, BBC, CNN, or Al Jazeera.

The region you mentioned, Kursk, is inside Russia, not Ukraine, and has seen attacks (drone strikes etc.), but no credible reports say North Korean "subunits" are fighting there.

Bottom line:

Be very cautious with posts like these — always double-check major war-related claims