South Korea’s state intelligence agency said Sunday that it is looking closely into a detailed tip that there have been casualties among North Korean troops in Russia.

This is the National Intelligence Service’s first official confirmation of related intelligence, despite similar claims from authorities in Western countries and the Ukrainian government via foreign media outlets.

Global Defense Corp, a website specializing in military affairs, reported on Saturday that 500 North Korean soldiers were killed Wednesday during Ukraine’s attack on Russia’s Kursk region with a Storm Shadow cruise missile. It didn't give a source. 

Citing authorities in the West, the Wall Street Journal reported on Thursday that a high-level North Korean general was injured during Ukraine’s air raid in Kursk.