Ukrainian President Volodymyr Zelensky this week confirmed reports of North Korean troops supporting Russians inside Ukraine, warning that the alliance between Moscow and Pyongyang is growing stronger and evolving beyond transferring weapons.
A Ukrainian military intelligence official, speaking on the condition of anonymity to discuss a sensitive security matter, told The Washington Post last week that "several thousand" North Korean infantry soldiers are undergoing training in Russia now and could be deployed to the front line in Ukraine by the end of this year.
South Korea's defense minister Kim Yong-hyun last week called the reports of North Korean military personnel helping Russia "highly likely." The Kremlin has dismissed the assertion as a "hoax."
"We see that the alliance between Russia and such regimes as the North Korean one is getting stronger," Zelensky said in his video address on Sunday. "This is not just about the transfer of weapons, this is in fact about the transfer of people from North Korea to the armed forces of the occupiers."
Why is North Korea sending its citizens to support Russia?
• North Korea has pledged 'full' support for Russia
North Korea has been one of the most vocal backers of Russia's war in Ukraine, with leader Kim Jong Un pledging "full" support for President Vladimir Putin's "sacred war for regional peace and international justice." In March 2022, a month after the invasion, North Korea was one of just four countries that joined Moscow to vote against a United Nations resolution condemning the aggression.
Since then, Pyongyang has been helping Putin by sending the old Soviet-era munitions that Russia desperately needs, according to U.S., Ukrainian and South Korean officials. U.S. officials say those shipments have included artillery shells and other weapons, and in return, North Korea may be receiving Russian help to advance its own weapons program.
North Korea's military ties with Moscow date back to the Soviet Union era, when Soviet leaders supported the North's invasion of the South, which sparked the 1950-53 Korean War. The war halted in a cease-fire, and both Koreas have maintained a stockpile of ammunition and weapons in case conflict resumes. As the conflict in Ukraine drags on, Russia is apparently turning to North Korea for those old shells and weapons. Both Pyongyang and Moscow have denied the allegations.
• Why would Pyongyang send military officers to the conflict?
Now there are reports that North Koreans may be sending military personnel to the Russian-occupied Ukrainian territory of Donbas. Some military officers may already have been killed and injured, according to reports that surfaced last week on Telegram channels and in the Ukrainian press.
The Ukrainian military intelligence official said that while there were North Korean combat troops in Russia, none were in the Donbas region and the officers who were killed did not directly participate in combat.
South Korean experts say it's plausible that Pyongyang would send military personnel to Russia, especially technical advisers to supervise the use of North Korean weapons on the ground.
Given reports that many of North Korea's shells are duds, and other issues with the weaponry that Pyongyang sent, it would make sense for North Korea to dispatch personnel to help with maintenance, management and evaluation of their weapons, said Lee Ho-ryung, North Korean military expert at the Korea Institute for Defense Analyses in Seoul.
"It is completely feasible that North Korea is dispatching not only military supplies but also engineers," Lee said.
This comes after Putin and Kim signed a mutual defense pact this summer, vowing to expand their military cooperation.
Sending personnel to help Russians use North Korean weapons could be a sign that the military cooperation between the two countries is deepening, experts say.
The Ukrainian official said Putin may have asked North Korea for help with personnel to avoid a new wave of mobilization to replenish his troops. North Korean troops could free up reserve troops who are within Russia, which could have "a significant impact" in certain areas on the front lines, the official said.
• What's in it for North Korea?
North Koreans may already be in Russia aiding with reconstruction efforts in Ukraine's Donbas region, according to Daily NK, a Seoul-based monitoring group with informants inside North Korea. Citing unnamed sources in North Korea and Russia, the outlet reported in April that Pyongyang sent about 150 new laborers there to help with rebuilding efforts.
As far back as 2022, Russian officials were publicly welcoming North Koreans helping mitigate the labor shortage caused by the war. "[North] Korean builders will be an asset in the serious task of restoring social, infrastructural and industrial facilities" in Donbas, Russia's ambassador to North Korea, Alexander Matsegora, told the pro-Kremlin daily Izvestia in the first year of the war.
Alexei Kolmakov, construction minister of Novosibirsk Oblast in Siberia, said last year that the region had requested to bring about 2,000 North Korean workers to address construction labor shortages in Siberia and the breakaway republic of Luhansk.
North Korea has a long history of sending workers - mainly lumberjacks and builders - to Russia to earn money for the cash-strapped regime.
Kim is especially desperate for cash after the pandemic, which forced him to close his borders even to China, cutting off the trade that keeps his economy afloat.
North Korea was already facing mounting international sanctions before covid, and its economy shrank from 2020 to 2023, according to South Korea's central bank. While trade with China has resumed since Kim began reopening borders in 2023, it has not yet reached pre-pandemic levels.
These workers provide a stream of valuable foreign currency that helps Kim and his rule. They often work long hours in dangerous conditions with little safety training or gear. The vast majority are men whose passports are confiscated once they enter Russia and whose wives and children must remain in North Korea to deter the men from trying to escape while abroad.
Last month, the Telegram-based Russian outlet Mash claimed that a North Korean construction worker in Khimki, in Moscow Oblast, fell off a scaffolding. The worker's supervisor transported him under a bridge and left him there to die, Mash reported.
• But didn't the U.N. ban North Korean labor exports?
North Koreans have continued to work in Russia and elsewhere despite a United Nations prohibition on governments issuing new work permits to North Koreans and requiring countries to repatriate all laborers by the end of 2019.
The U.N. Security Council targeted the worker program, which has long subsidized Kim's nuclear ambitions, as a part of sanctions placed on Pyongyang after its sixth nuclear test. Russia criticized the sanctions but agreed to adhere to them.
But North Koreans remained in Russia, including those who could not return home after North Korea's borders were closed in 2020, The Post found.
After the U.N. ban, North Koreans continued to enter Russia with tourist or student visas and work for Russian companies, according to the South Korean Unification Ministry's 2024 report based on escapees' testimonies.
Michelle Ye Hee Lee is The Washington Post's Tokyo bureau chief, covering Japan and the Korean peninsula.