"In December, they (North Korean troops) engaged in actual combat, during which at least 100 fatalities occurred," Lee said, speaking after a briefing by South Korea's spy agency. "The National Intelligence Service also reported that the number of injured is expected to reach nearly 1,000."

Despite those losses, the agency also said it had detected signs North Korean leader Kim Jong Un was preparing to train a new special operations force to ship westward. Lee noted that the North's elite Storm Corps -- from which the initial deployment was drawn -- had "the capacity to send reinforcements". The NIS also predicted "that Russia might offer reciprocal benefits" for a new deployment, Lee said, including "modernising North Korea's conventional weaponry".

The lawmaker added that "several North Korean casualties" had already been attributed to Ukrainian missile and drone attacks and training accidents, with the highest ranking "at least at the level of a general". The NIS said the high number of casualties could be attributed to the "unfamiliar battlefield environment, where North Korean forces are being utilised as expendable frontline assault units, and their lack of capability to counter drone attacks," said Lee.

"Within the Russian military, complaints have reportedly surfaced that the North Korean troops, due to their lack of knowledge about drones, are more of a burden than an asset," Lee said. His comments follow a senior US military official on Tuesday saying North Korean forces had suffered "several hundred" casualties fighting Ukrainian troops in Russia's Kursk region.

Ukrainian commander-in-chief Oleksandr Syrsky previously said North Korean troops had been at the heart of an "intensive offensive" in Kursk.