North Korean soldiers “disguised” as Russian fighters from Siberia have clashed with Ukrainian troops, Kiev's defense minister said, although the number of casualties among Pyongyang's forces remains unclear.

North Korean troops stationed alongside Moscow's own forces were dressed to look like Russian recruits from the eastern Siberian region of Buryatia, Rustem Umerov told South Korean broadcaster KBS.

Ukrainian, South Korean and Western intelligence agencies have said in recent weeks that North Korea is sending between 10,000 and 12,000 troops to Russia to bolster Moscow's war efforts against Kiev.

Umerov said there had been “small clashes” between Ukrainian and North Korean troops so far, but that Ukraine could not yet verify how many casualties North Korea had suffered or how many soldiers had become prisoners of war.

This was announced by an unnamed Ukrainian official The New York Times An article published Tuesday said North Korean troop deployments were limited and likely intended to test Ukraine's lines for vulnerabilities.

Pyongyang's troops joined Russia's 810th Separate Marine Infantry Brigade, the official said. The U.S.-based think tank Institute for the Study of War (ISW) said on Tuesday that Russia was likely trying to integrate the North Korean fighters into Russia's military structure rather than “letting individual North Korean units fight under Russian command.” “

A US official said this Just A significant number of North Korean troops were killed, but no further details were provided.

“We have identified contacts with North Korean forces, but expect further operations in the coming weeks and will analyze and review them accordingly,” Umerov added.

He said up to 15,000 troops could ultimately support Russian forces in Russia's southern Kursk region, where Moscow has been fighting since early August to wrest control of part of Russian territory near the border from Ukraine.

The Pentagon said on Monday that 10,000 North Korean soldiers were in Kursk. In late October, U.S. Defense Secretary Lloyd Austin said the U.S. had not yet detected North Korean troops engaged in fighting but that they would “join the fight against Ukraine in the coming days.”

Many Western countries have denounced the arrival of North Korean troops to fight in Europe's biggest land war since World War II as a dangerous escalation of the bitter and bloody conflict.

“The first battles with North Korean soldiers open a new page of instability in the world,” Ukrainian President Volodymyr Zelensky said in his evening address on Tuesday. “We must do everything we can to ensure that this move by Russia to expand the war – to really escalate it – fails.”

Andriy Kovalenko, the head of the counter-disinformation department at Ukraine's National Security and Defense Council, said on Monday that North Korea's first troops in Kursk had “already come under fire.”

The following day, Kovalenko said North Koreans were “in Russian military uniform” alongside Russian units in Kursk and learned how to use various types of drones against Ukrainian forces. The US had previously said Moscow had provided North Korean troops with Russian military uniforms.

South Korea's National Intelligence Service said last month that an initial group of 1,500 North Korean fighters traveled to Russia and were provided with Russian military uniforms, Russian-made weapons and fake documents showing the fighters were living in regions of Siberia .

“We expect further engagements in the coming weeks,” said Umerov.

Pyongyang has supplied Moscow with a significant number of rockets and millions of shells. According to the head of Kiev's military intelligence, his support makes North Korea Russia's most dangerous ally with which Ukraine has to contend. In recent months, Kiev has persistently attacked ammunition depots storing North Korean ammunition.