North Korea has been supplying a vast amount of artillery and other conventional weapons to Russia, and last October it sent about 10,000-12,000 troops to Russia as well, according to U.S., South Korean and Ukraine intelligence. Seoul, Washington and others worry Russia could in return transfer to North Korea sophisticated weapons technologies that can enhance its nuclear program.

South Korea’s military said Friday it suspects North Korea is preparing to send additional troops to Russia after its soldiers fighting in the Russian-Ukraine war suffered heavy casualties. South Korea’s Joint Chiefs of Staff also assessed in a report distributed to journalists that North Korea is continuing its preparations to test-fire an intercontinental ballistic missile intended to reach the United States.

Although Moscow and Pyongyang initially dismissed reports about the North's troop deployment, Russian President Vladimir Putin in October did not deny that North Korean soldiers were in Russia and a North Korean official said any such deployment would be lawful.