The North Korean forces fighting for Russia in Kursk have not been seen since mid-January, according to South Korea's intelligence agency for AFP.
According to the intelligence agency, this could be due to "heavy losses, but the details are still being investigated", the agency says in a statement.
In late January, similar information came from Ukraine's intelligence agency.
Intelligence agencies in Ukraine, the USA, and South Korea have previously claimed to have evidence that more than 10,000 soldiers from North Korea have fought on Russia's behalf in the western part of the country. Ukraine launched an offensive against Russian Kursk in August.
Neither Moscow nor Pyongyang has confirmed the North Korean presence in Russia.
