South Korea summons Russia’s ambassador over Pyongyang’s alleged deployment of soldiers in support of Moscow’s war in Ukraine.

South Korea has summoned Russia’s ambassador to criticize Pyongyang’s decision to send hundreds of soldiers to support Moscow’s war in Ukraine, the Foreign Ministry said as it called for their immediate withdrawal.

In Pyongyang’s first such deployment abroad, about 1,500 special forces soldiers have arrived in Russia and are likely to head to the front lines after acclimatization, Seoul’s spy agency said on Friday, adding that more troops would leave soon.

South Korea has long accused the nuclear-armed North of supplying weapons to Russia for use in Ukraine, and the North’s leader Kim Jong Un signed a military deal with Russian President Vladimir Putin in June.

Seoul expressed its “serious concerns over North Korea’s recent deployment of troops to Russia and strongly urged the immediate withdrawal of North Korean forces,” Vice Foreign Minister Kim Hong-kyun told Russia’s ambassador on Monday Georgiy Zinoviev.

Seoul’s spy agency released detailed satellite images showing it was the first group of 1,500 North Korean special forces from the elite Storm Corps to arrive in Vladivostok on Russian military ships.

Any military cooperation between the two countries violates multiple United Nations Security Council resolutions, Vice Foreign Minister Kim said.

“We condemn in the strongest terms North Korea’s illegal military cooperation, including the sending of troops to Russia,” the State Department quoted him as saying.

“We will respond together with the international community by mobilizing all available resources against acts that threaten our fundamental security interests.”

Zinoviev “stressed that cooperation between Russia and North Korea … is not against the interests of South Korea’s security,” the Russian embassy said in a statement.

Kremlin spokesman Dmitry Peskov also said Monday that Moscow “will continue to develop this cooperation.”

“North Korea is our closest neighbor and partner, and we are developing relations in all areas, and it is our sovereign right,” he told journalists in Moscow, declining to comment on whether Russia is using North Korean troops .

Later on Monday, South Korean President Yoon Suk-yeol spoke to NATO chief Mark Rutte and urged the alliance to take “concrete countermeasures” against growing Russian-North Korean cooperation.

NATO has not yet confirmed the North Korean troop deployment, but Rutte said in a message on X that it would represent “a significant escalation” of the conflict.

British Foreign Secretary 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, Yoon’s office said.

Ukrainian President Volodymyr Zelensky has accused Pyongyang of sending 10,000 soldiers to Russia and called for a strong international response on Sunday.

The United States said Friday it could not confirm reports that North Korean troops were fighting, but said if true it would be a “dangerous development” in Russia’s war against Ukraine.