This handout image from South Korea's National Intelligence Service (NIS), released Oct. 18, shows an undated satellite image by Maxar Technologies of what NIS said is the Russian vessel Angara, loaded with North Korean weapons, departing from Rajin Port in the North Korean city of Rason. AFP

There is increasing evidence that North Korea has sent troops to Russia for possible deployment in Ukraine, a move that could further escalate the war in Ukraine and ratchet up tensions on the Korean Peninsula.

South Korea's spy agency said Wednesday that it believes North Korea has sent 3,000 troops to Russia and aims to provide a total of 10,000 troops by December.

"About 3,000 North Korean soldiers sent to Russia have been split among multiple military bases. The National Intelligence Service (NIS) believes they have yet to be deployed in battle," Rep. Park Sun-won, a member of the National Assembly Intelligence Committee, said after a briefing by NIS chief Cho Tae-yong.

Hours later, the White House confirmed that the U.S. believes at least 3,000 North Korean troops are undergoing training at military bases in the Russian Far East. Russia and North Korea have neither confirmed nor denied reports that North Korea has sent troops to Russia. North Korea said Friday that the dispatch of its troops, if true, would be in line with international law. Russian President Vladimir Putin said it was up to Moscow how to run its mutual defense clause with Pyongyang.

Experts noted that it is quite unusual for the U.S., a country with extensive intelligence capabilities, to confirm the reports days after Ukraine and South Korea acknowledged the presence of North Korean troops in Russia.

"I believe the U.S. has delayed the announcement due to internal circumstances. The U.S. simply restated what the NIS said without specifying or elaborating further. The U.S. has been investing its diplomatic efforts in the Middle East, but its mediation efforts have not been fruitful so far. It wouldn't want to risk another clash in Ukraine as it can affect votes in swing states ahead of the U.S. presidential election," said Doo Jin-ho, a research fellow at the Center for Security and Strategy in the Korea Institute for Defense Analyses.

North Korea has deployed military personnel and technicians to foreign conflict zones, including Angola, Egypt and Syria, in the past to provide its elite military forces with battle experience.

"North Korea sent pilots to fight for North Vietnam during the Vietnam War and deployed small-scale troops to Africa in the 1970s and 1980s. If reports about North Korean troops in Russia are true, it would be the highest number of North Korean troops abroad," said Kim Dong-yup, a professor at the University of North Korean Studies.

It has also been a major supplier of rockets and missiles to Hezbollah since the 1980s, and provided the Lebanese Shiite organization with military support in the lead-up to the 2006 Israel-Lebanon war.

This time, North Korea is believed to have dispatched its special forces to Russia for training. A video circulating on social media showed North Korean soldiers receiving uniforms and equipment at a training ground in the Russian Far East.

A captured image of video released by the Centre for Strategic Communication and Information Security of Ukraine (SPRAVDI) shows soldiers, presumed to be from North Korea, lining up to receive Russian supplies. Captured from SPRAVDI's X account

"The special elite forces are believed to possess physical prowess compared to conventional troops. I think North Korean soldiers will learn how to use military equipment such as drones, participate in guerilla activities in the rear and block terrorist attacks. I think it would first undergo training and gain combat experience in Russia's Kursk region," Doo said.

Experts fear North Korea may escalate provocations against South Korea and pose a greater threat to national security by leveraging its battlefield experience.

"What concerns us most is that North Koreans will be able to gain real-life battle experience to complement their years of military training. This poses a serious threat to our national security," said Yang Uk, a military expert at the Asan Institute for Policy Studies.

The reclusive regime is likely to gain not only battle experience but also money and technology from sending troops to support Russia. The NIS said each North Korean soldier would receive around $2,000 per month for their service in Russia.

"North Korea would be able to gain economic support from Russia, but what's more important is that we will be seeing a stronger military alliance between Russia and North Korea. In the long term, North Korea could take up Russia's supply chain that may lay the foundation for the country's development including its weapons systems and defense industry," Yang said.

On Thursday, Russia's parliament ratified its bilateral treaty with North Korea that calls for mutual commitment to providing military assistance to each other in the event of an armed attack, according to Russian news agency TASS.

"Pyongyang will seek advanced military technology from Moscow including technical assistance for development of intercontinental ballistic missiles, submarine-launched ballistic missiles, hypersonic ballistic missiles as well as satellite technology," Doo said. "North Korea may also ask Russia to provide extended deterrence."

This image, captured from a video released on Telegram by Astra, an independent Russian media outlet, shows a group of soldiers believed to be North Koreans dispatched to Russia gathered at an unknown location. Yonhap

Experts advised the government to take a more cautious approach and warned officials to not use the issue for internal politics.

"Our future hinges on the actions we take. We must refrain from making premature assumptions while it remains unclear what North Korean troops will do with Russian military. Supplying lethal weapons to Ukraine can sever our diplomatic ties with Russia. As a divided nation, we need to fortify strategic autonomy and manage relations with China and Russia for stability on the Korean Peninsula," Kim said.

Doo said the government should make efforts to sustain strategic communication with Russia. "Whether we want it or not, we could be dragged into the war based on the U.S. and NATO's decisions. The presidential office or the national intelligence agency should communicate with Russia behind the scenes to prevent conflicts from escalating," he said.