South Korean President Yoon Suk Yeol speaks during a joint press conference with Polish President Andrzej Duda (not seen in photo) at the presidential office in Seoul, South Korea on Thursday.

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SEOUL – South Korea’s president vowed Thursday to respond to North Korea’s troop deployment in Russia, including by possibly supplying offensive weapons to Ukraine.

Seoul will not “remain inactive” in the face of a North Korean “provocation that threatens global security beyond the Korean Peninsula and Europe,” South Korean President Yoon Suk Yeol told reporters in Seoul after a summit with visiting Polish President Andrzej Duda.

Yoon’s comments follow Defense Secretary Lloyd Austin’s assertion Wednesday that the United States has evidence of North Korea’s deployment of troops to Russia.

Austin did not specify what the evidence was, but said that if North Korean troops were fighting for Russia, it would be a “very, very serious issue.”

South Korea’s intelligence chief told lawmakers on Wednesday that North Korea has sent 3,000 troops, including special forces, to Russia for training, and that the North plans to increase that number to 10,000 by December.

The deployment of North Korean troops could heighten concerns that the war could spill over and affect tensions in Asia, from the Korean Peninsula to the Taiwan Strait.

South Korean intelligence said last week that North Korea has sent more than 13,000 containers of artillery, missiles and other conventional weapons to Russia since August 2023. Ukrainian President Volodymyr Zelensky warned earlier this month that North Korea is “no longer just about transferring weapons” but also personnel to help Russian forces.

President Yoon pledged support for additional South Korean arms sales to Poland, including the sale of K2 tanks worth $7 billion. So far, South Korea has helped Ukraine by supplying weapons to the United States and Ukraine’s neighbors, but he said this could change.

“We have applied the principle of not directly supplying lethal weapons” to fighters, he told reporters, “but we can be more flexible and revise the policy depending on North Korea’s military activities.”

Even if they fight on the front lines, analysts believe North Korean troops will be relegated to a supporting role in the war.

Lee Ho-ryung, a researcher at the Korea Institute for Defense Analyses, a government think tank in Seoul, says North Korean troops could be sent to blunt the Ukrainian offensive in Russia’s Kursk region.

The North Koreans will probably initially be “in charge of security and the like.” But as time goes on, and with training, they may be able to support Russian operations,” Lee said. “It is then expected that there will be many casualties during that process.”

South Korean Defense Minister Kim Yong-hyun told lawmakers on Thursday that North Korean troops “are considered mere cannon fodder mercenaries.” North Korean leader Kim Jong Un, he added, “has sold out his people’s military for an illegal war of aggression.”

North Korean state media has made no mention of deploying troops to Russia, and South Korean intelligence says North Korea may seize family members of troops sent to Russia, possibly to calm domestic discontent over the deployment suppress.

Even if the North Korean deployment has limited military value, analysts say it sends important messages to the major powers.

North Korea has named Russia a top foreign policy priority and signed a treaty in June, ratified by the Russian parliament on Thursday, that allows for mutual aid if either country is attacked. Deploying troops can be seen as sealing that deal.

For Ukraine, pointing to the North Korean intervention strengthens the Ukrainian government’s call for Western military aid. South Korea’s suggestion that it could arm Ukraine is music to Kiev’s ears, argues Yoon Sukjoon, a senior research fellow at the Korea Institute for Maritime Strategy, and a retired South Korean navy captain.

“If South Korea says, ‘We will now side with the US and sell offensive weapons to Ukraine,’ it helps Ukraine,” he says, “and I think ultimately this is what Ukraine wanted to achieve with the revelation of President Zelenskiy on the North Korean deployment.

That said, Yoon and other analysts believe South Korea will respond cautiously to any North Korean troop deployment, to prevent Russia from giving North Korea the military aid it seeks as a reward for sending troops.

Moscow has warned Seoul not to get involved in Ukraine. “It is necessary to think about the consequences for the security of South Korea” if the country were to enter the conflict in Ukraine, Russian Foreign Ministry spokesperson Maria Zakharova said on Wednesday. “The Russian Federation will respond firmly to any steps that could threaten the security of the country and its citizens.”

Se Eun Gong contributed to this report from Seoul.