Seoul demands 'immediate withdrawal' of North Korean troops in Russia

South Korea summoned the Russian ambassador on Monday to criticise Pyongyang's decision to send thousands of soldiers to support Moscow's war in Ukraine, the foreign ministry said, calling for their immediate withdrawal.

About 1,500 North Korean special forces soldiers are already in Russia acclimatising and likely to head to the front lines, Seoul's spy agency said Friday, with additional troops set to depart soon, Pyongyang's first such deployment overseas.

South Korea has long claimed the nuclear-armed North is supplying Russia with weapons for use in Ukraine, and Seoul expressed alarm over the troop deployment, which comes after Kim Jong Un and Russian President Vladimir Putin signed a military deal in June.

Seoul expressed its "grave concerns regarding North Korea's recent dispatch of troops to Russia and strongly urged the immediate withdrawal of North Korean forces", vice foreign minister Kim Hong-kyun told Russian ambassador Georgiy Zinoviev.

Seoul's spy agency released detailed satellite images showing the first batch of 1,500 North Korean special forces from the elite "Storm Corps" had arrived in Vladivostok on Russian military vessels.

Any military cooperation between the two countries violates multiple Security Council resolutions, Kim said.

Russian ambassador Zinovyev "stressed that cooperation between Russia and North Korea... is not directed against the interests of South Korea's security", the embassy said in a statement.

Also on Monday, South Korea's President Yoon Suk Yeol spoke to Nato chief Mark Rutte, urging the alliance to take "concrete countermeasures" against growing Russia-North Korea cooperation.

Nato, which has not yet confirmed the North Korean troop deployments, said that it "would mark a significant escalation" in the conflict, Rutte said on X.

British foreign minister David Lammy, who was in Seoul on Monday, called Russia's actions "reckless and illegal" and added that London would work with Seoul to respond, according to Yoon's office.

"South Korea's protest to Russia will not change anything regarding Moscow's military cooperation with the North," said Cheong Seong-chang, director of the Korean peninsula strategy at Sejong Institute.

In return for sending soldiers to help Russia in Ukraine, "Kim Jong Un is aiming to acquire military technologies, ranging from surveillance satellites to submarines", he said.