South Korea’s spy agency has said that North Korea appears to have sent additional troops to Russia, after its soldiers deployed on the Russian-Ukraine fronts suffered heavy casualties.

The National Intelligence Service (NIS) said in a brief statement it was trying to determine exactly how many more troops North Korea has deployed to Russia.

The NIS also assessed that North Korean troops were redeployed at fronts in Russia’s Kursk region in the first week of February, following a reported temporary withdrawal from the area.

Ukrainian President Volodymyr Zelensky, in an address on February 7, confirmed a new Ukrainian offensive in Kursk and said North Korean troops were fighting alongside Russian forces there.

Observers say North Korean leader Kim Jong Un could send more troops to Russia to win further Russian assistance before the war ends (Korean Central News Agency/Korea News Service via AP)

North Korea has been supplying a vast amount of conventional weapons to Russia, and last autumn it sent about 10,000-12,000 troops to Russia as well, according to US, South Korean and Ukraine intelligence officials.

North Korean soldiers are highly disciplined and well trained, but observers say they have become easy targets for drone and artillery attacks on Russian-Ukraine battlefields due to their lack of combat experience and unfamiliarity with the terrain.

In January, the NIS said about 300 North Korean soldiers had died and another 2,700 had been injured. Mr Zelensky earlier put the number of killed or wounded North Koreans at 4,000, though US estimates were lower at around 1,200.

Earlier on Thursday, South Korea’s JoongAng Ilbo newspaper, citing unidentified sources, reported that an additional 1,000-3,000 North Korean soldiers were deployed to Kursk between January and February.

Ukrainian President Volodymyr Zelensky said North Korean troops were fighting alongside Russian forces in Kursk (AP/Evgeniy Maloletka)

South Korea, the US and their partners worry that Russia could reward North Korea by transferring high-tech weapons technologies that can sharply enhance its nuclear weapons programme. North Korea is expected to receive economic and other assistance from Russia as well.

During talks in Saudi Arabia last week, Russia and the US agreed to start working towards ending the war and improving their diplomatic and economic ties.

Ukrainian officials were not present at the talks. That marked an extraordinary shift in US foreign policy under President Donald Trump and a clear departure from US-led efforts to isolate Russia over its war in Ukraine.

Observers say North Korean leader Kim Jong Un could send more troops to Russia to win further Russian assistance before the war ends.