North Korean leader Kim Jong Un and Russia's President Vladimir Putin shake hands after signing a comprehensive strategic partnership in Pyongyang, North Korea in June this year.
CNN  — 

North Korea has shipped 1,500 soldiers to Russia for training, South Korea’s spy agency said on Friday, describing the move as the first step in the secretive state’s military involvement in Moscow’s war against Ukraine.

The hermit nation transported its special forces fighters on seven Russian ships earlier in October, South Korea’s National Intelligence Service (NIS) said in a press release on Friday.

Those units had previously been personally inspected by North Korean leader Kim Jong Un, the agency added.

Large Russian transport aircraft have also been frequently traveling between Vladivostok and Pyongyang, it said.

The revelations follow repeated warnings from Ukrainian President Volodymyr Zelensky that the growing alliance between Russia and North Korea has resulted in North Korean troops joining the war.

“From intelligence that I have … they are preparing 10,000 soldiers, different soldiers, land forces, technical personal,” Zelensky told reporters at a NATO summit in Brussels on Thursday.

“We know about 10,000 soldiers of North Korea … are preparing to (start) fighting against us. This is really an urgent thing, I spoke about it with the United States, I spoke about it with all the leaders.”

South Korean media reported that the North will send a total of 12,000 troops, although this figure was not included in the NIS statement.

The intervention could mark the first time that North Korea has participated in a major way in an international war. The state has one of the largest militaries in the world, with 1.2 million soldiers, but those troops lack combat experience.

The NIS statement on Friday said the troops had been shipped to areas deep in Russia’s far east, near its border with the secretive nation, and “are expected to be deployed to the front lines once their adaptation training is completed.”

It added that soldiers were supplied with Russian military uniforms and Russian-made weapons, and they were issued forged identification documents of Siberian residents with similar appearances to North Koreans, likely to disguise themselves as Russian soldiers and conceal their involvement on the battlefield.

Kremlin spokesman Dmitry Peskov last week dismissed allegations that North Korean personnel had been sent to help Russia as “another hoax.”

Multiple governments have accused Pyongyang of supplying arms to Moscow for its grinding war in Ukraine, a charge both countries have denied, despite significant evidence of such transfers.

The two nations, both pariahs in the West, have forged increasingly warm ties since Russia’s invasion.

During Putin’s visit to the North Korean capital in June, the two countries pledged to use all available means to provide immediate military assistance in the event the other is attacked, part of a landmark defense pact agreed by the autocratic nations.

Putin said during that trip that the two countries were ramping up ties to a “new level.”

In remarks ahead of talks between the two, North Korean leader Kim Jong Un voiced his “full support and solidarity with the struggles of the Russian government, military and the people,” pointing specifically to Moscow’s war in Ukraine “to protect its own sovereignty, safety and territorial stability.”