At least 100 North Korean troops deployed to Russia have been killed, with another 1,000 injured in combat against Ukrainian forces in intense fighting in the Kursk region, a South Korean lawmaker said on Thursday citing the country's spy agency.

The heavy losses are attributed to the lack of experience by North Korean troops in drone warfare and unfamiliarity with the open terrain where they are taking part in the battle, a member of parliament Lee Seong-kweun told reporters.

Lee was speaking after a closed-door briefing by the National Intelligence Service (NIS) to parliament.