South Korea has summoned the Russian ambassador, urging an “immediate withdrawal” of North Korean troops reportedly being trained for combat in Ukraine. According to South Korea’s intelligence agency, approximately 1,500 North Korean soldiers, including special forces, have already arrived in Russia.

During a meeting with Ambassador Georgiy Zinoviev, South Korea’s Vice Foreign Minister Kim Hong-kyun condemned this development, emphasizing that Seoul will respond with “all measures available.” In his response, Zinoviev acknowledged the concerns but asserted that the cooperation between Moscow and Pyongyang operates “within the framework of international law.” However, he did not clarify what specific cooperation he was referencing, nor did he confirm allegations regarding North Korean troop deployments.

Later, Kremlin spokesperson Dmitry Peskov reassured reporters that the cooperation between Russia and North Korea is “not directed against third countries” and “should not worry anyone,” according to Russian state news agency Tass. Pyongyang has not issued any comments on the allegations.

For years, South Korea has accused the North of supplying weaponry to Russia for its war efforts in Ukraine, but officials suggest that the current situation surpasses merely transferring military materials. Some South Korean media outlets have indicated that as many as 12,000 North Korean soldiers may be deployed.

“This not only gravely threatens South Korea but also the international community,” Kim stated on Monday. Following their leaders’ signing of a security pact in June, which promises mutual support in case of aggression, Moscow and Pyongyang have intensified their cooperation. Last week, Putin introduced legislation to ratify this agreement.

NATO Secretary-General Mark Rutte noted that North Korea’s troop involvement with Russia “would mark a significant escalation” in the ongoing conflict. In a conversation with Rutte, South Korean President Yoon Suk Yeol urged NATO to consider “concrete countermeasures” and announced plans to bolster security cooperation among South Korea, Ukraine, and NATO.

British Foreign Minister David Lammy, currently visiting Seoul, characterized Russia’s actions as “reckless and illegal,” affirming that London will collaborate with Seoul in response, as reported by Yoon’s office. The United States and Japan have also condemned the strengthening military ties between North Korea and Russia.

Responding to a BBC inquiry about the alleged collaboration, Chinese foreign ministry spokesperson Lin Jian expressed hopes that all parties involved would work to de-escalate the situation and seek a political solution to the Ukraine crisis.

Defense analysts have suggested that North Korea’s involvement could complicate the conflict. Moon Seong-mok from the Korea National Strategy Institute commented, “North Korea’s involvement could open the door for greater international participation in the conflict, potentially drawing in more countries.” He added that the international community might escalate sanctions and pressure on both Russia and North Korea, though the actual benefits of North Korea’s involvement remain uncertain.

Other experts, however, contend that integrating North Korean troops into Russian military units could be problematic. They cite language barriers and the lack of recent combat experience among North Korean soldiers as potential hurdles. Valeriy Ryabykh, editor of the Ukrainian publication Defence Express, suggested that North Korean troops might mostly be assigned to guard sections of the Russian-Ukrainian border, freeing up other Russian units for frontline engagements. “I would rule out the possibility that these units will immediately appear on the front line,” he stated.

This report includes contributions from Sangmi Han, Jake Kwon, and Hosu Lee in Seoul.