North Korean leader Kim Jong-un (on carpet) inspects an honor guard during a visit to the North Korean Army's 2nd Corps Headquarters, Oct. 17, in this photo provided by the North's official Korean Central News Agency. Kim stressed again that South Korea is a foreign country and an apparent hostile country, according to the news agency. Yonhap

North Korea's large-scale provision of troops to Russia in its war against Ukraine is seen as a grave development that could further destabilize the global security landscape marred by conflicts, as well as a blow to the fragile diplomatic ties between Seoul and Moscow.

On Friday, South Korea's spy agency confirmed the North has decided to send around 12,000 troops to support Russia in the war and has already begun deployment of approximately 1,500 North Korean soldiers to Vladivostok.

The National Intelligence Service's (NIS) announcement confirms monthslong speculation over the growing military cooperation between Moscow and Pyongyang, mainly involving a suspected arms trade.

This marked the first time the North has deployed ground forces in large scale, though it has dispatched a small number of trainers before as a way to earn foreign currency.

The deployment of such a large contingent of North Korean troops, including its most elite military units, signals a major development in its military ties with Russia, which was previously limited to supplying artillery shells and short-range ballistic missiles.

Observers say Pyongyang and Moscow will likely push forward their partnership, with the latest deployment serving as a clear demonstration of the treaty signed by Russian President Vladimir Putin and North Korean leader Kim Jong-un during their summit in Pyongyang in June.

The treaty includes a mutual defense clause, under which each side agreed to provide mutual assistance in the event of aggression against one of the countries.

Security experts in Seoul have also raised concerns that Pyongyang in return could receive key missile technology from Russia that the North has not secured yet, including that involving intercontinental ballistic missile reentry.

Hong Min, a senior research fellow at the Korea Institute for National Unification, said the deployment itself is symbolic and sends the message that North Korea is fighting alongside Russia.

"That could put a lot of pressure on Russia to give in return," he said.

In response, South Korea could move toward considering providing lethal weapons in support of Ukraine in the ongoing war, and thus further strain the ties between Seoul and Moscow since the Ukraine war.

Hyun Seung-soo, deputy director of the Korea Institute for National Unification, stated, "If South Korea directly provides lethal weapons to Ukraine without going through third countries like the U.S., it would drastically change the security dynamics on the Korean Peninsula."

"In such a case, Russia will not sit idly by in response, and the South Korea-Russia relationship could reach an irreparable state," Hyun said.

Following an emergency security meeting convened by President Yoon Suk Yeol on the issue Friday, the presidential office vowed to respond by mobilizing "all available means" in cooperation with the international community.

Other observers point out the North is likely to engage in stronger provocations with Russia at its back, further intensifying its rivalry with the South Korea-U.S. alliance. (Yonhap)