Russia took steps on Thursday to ratify a significant defense agreement with North Korea, prompting South Korea to issue a warning that it would not remain passive if Pyongyang sent thousands of troops to assist Moscow in its conflict with Ukraine.

According to South Korea’s intelligence agency, a substantial number of North Korean soldiers are currently undergoing training in Russia and are expected to be deployed to the front lines in Ukraine shortly, with additional troops anticipated by December.

On Thursday, lawmakers in Russia’s lower house of parliament voted unanimously to ratify the treaty with North Korea, which stipulates “mutual assistance” in the event of aggression against either party.

The agreement will now proceed to the Federation Council, the upper house, for final approval. Both chambers of parliament typically serve to endorse decisions made by the Kremlin.

Western nations suspect that North Korea is already supplying Moscow with weaponry for its operations in Ukraine.

In response to the potential troop deployments from Pyongyang, South Korean President Yoon Suk Yeol stated, following discussions with Polish President Andrzej Duda, that South Korea would not remain passive in this situation.

The two nations concurred that North Korea’s military actions represent “a provocation that endangers global security beyond both the Korean Peninsula and Europe,” he stated. South Korea, recognized as one of the top ten arms exporters globally, has historically resisted pressure from allies, including the United States, to provide military support to Kyiv.

However, it has suggested a potential reassessment of this stance in response to North Korea’s provocations, with President Yoon indicating on Thursday that Seoul would “take necessary actions in collaboration with the international community” to address the situation.

Since Russia initiated its military campaign in Ukraine in 2022, the ties between Pyongyang and Moscow have strengthened. North Korean leader Kim Jong Un has referred to Russian President Vladimir Putin as his nation’s “dearest friend.”

On Wednesday, Moscow declined to confirm or deny reports regarding the deployment of North Korean soldiers to Russia, advising reporters to “inquire with Pyongyang” about the whereabouts of its troops.

Seoul has already exported billions of dollars worth of tanks, howitzers, attack aircraft, and rocket launchers to Poland, a significant ally of Kyiv.

In June, South Korea reached an agreement to share the necessary expertise for the construction of K2 tanks with Poland, a move that experts believe could significantly advance production capabilities within Ukraine. President Yoon emphasized that both nations will “actively support the successful progress of the Korea-Poland defense cooperation.” This initiative is expected to include the signing of a second contract for South Korean K2 tanks by the year’s end.

Additionally, the two countries pledged to “enhance collaborative efforts for the restoration of peace and reconstruction in Ukraine” and to “continue expanding support for the Ukrainian people while closely collaborating with Poland throughout this process.”

President Duda’s four-day visit to South Korea will conclude on Friday, featuring visits to Hyundai Rotem, the manufacturer of the K2 tanks, and Hanwha Aerospace, the largest defense contractor in South Korea. Hanwha Aerospace has also finalized a $1.64 billion agreement with Poland to provide rocket artillery systems.

A South Korean official from the presidential office informed reporters on Tuesday that Seoul is prepared to provide Ukraine with defensive weaponry, and may consider supplying offensive weapons if the situation escalates.

Before the meeting between Yoon and Duda, a North Korean balloon carrying refuse landed in the presidential compound in Seoul. Local news outlets reported that the balloon contained propaganda leaflets mocking the South Korean president and his spouse.

Images released by the media displayed a leaflet featuring a picture of South Korean first lady Kim Keon Hee, accompanied by the phrase: “Queen Kim Keon Hee, a figure who rivals Marie Antoinette, the epitome of luxury and indulgence.”