Kim Jong-un's soldiers, who have been fighting in Russia's Kursk region against the Ukrainian army, are said to have suffered heavy losses.
North Korea appears to have sent 3,000 more soldiers to Russia as part of its continued support for Moscow’s war against Ukraine, South Korea has said.
The troops were deployed in January and February, according to Seoul’s latest military assessment.
South Korea’s Joint Chiefs of Staff also said that North Korea had provided the Russian army with a “considerable amount” of short-range ballistic missiles, self-propelled howitzers and rocket launchers.
Pyongyang is thought to have dispatched 11,000 of its soldiers last year to Russia’s Kursk region, parts of which were seized by Ukraine in a surprise offensive in August.
Reports later suggested that these North Korean fighters were temporarily taken off the frontlines in January after suffering heavy losses.
Seoul estimates that around 4,000 of Pyongyang’s soldiers have been killed or wounded so far fighting for Russia.
North Korean leader Kim Jong-un expressed his unwavering commitment to Russia last week during a visit from Sergei Shoigu, a top Kremlin security official.
Kim told Shoigu, who is a former Russian defence minister, that his country will continue to “invariably support Russia”.
Shoigu expressed gratitude for North Korea’s “solidarity with Russia’s position on all critical geopolitical issues, particularly on the Ukrainian issue”.
The two countries agreed to a landmark defence pact in 2024, with each promising to send military assistance to the other in the event that it is attacked.
South Korea’s announcement on Thursday about Pyongyang’s latest deployment of troops to Russia comes as European leaders meet in Paris to discuss aid and security guarantees for Ukraine.
The so-called “coalition of the willing” hopes to bolster Ukraine at a time when the US is attempting to broker a ceasefire between Moscow and Kyiv.
The White House announced earlier this week that both sides backed a ceasefire in the Black Sea.
However, Russia then said the deal would only hold if some Western sanctions were lifted, something Ukrainian President Volodymyr Zelenskyy claimed was not part of the agreement.