Ukrainian President Volodymyr Zelenskiy called on allies on Tuesday "not to hide" and to respond to evidence of North Korean involvement in Russia's war in Ukraine.
He said in his nightly address that Ukraine had information about the preparation of two units - possibly up to 12,000 North Korean troops - to take part in the war alongside Russian forces.
"This is a challenge, but we know how to respond to this challenge. It is important that partners do not hide from this challenge as well," Zelenskiy said.
The head of Ukraine's Main Directorate of Intelligence told the US publication "The War Zone" that Kyiv expected North Korean forces to turn up on Wednesday in Russia's southern Kursk region, where Ukrainian forces launched an incursion in August.
"We are waiting for the first units tomorrow in the Kursk direction, Lieutenant General Kyrylo Budanov told the media outlet. "It is unclear at the moment how many or how they will be equipped. We will see after a couple of days."
In his remarks, Zelenskiy said neither North Korea nor Russia took any account of the number of dead in a conflict.
"But all of us in the world have an equal interest in ending the war, not in prolonging it. We must therefore stop Russia and its accomplices," he said.
"If North Korea can intervene in a war in Europe, then the pressure on this regime is definitely insufficient."
British Defence Secretary John Healey said on Tuesday it was "highly likely" that North Korea had begun sending hundreds of troops to help Russia in the more than 2-1/2-year-old conflict.
A senior official at South Korean President Yoon Suk Yeol's office said Seoul may consider directly supplying weapons to Ukraine as part of measures to counter military ties between North Korea and Russia.
A top US diplomat said on Monday that Washington was consulting with its allies on the implications of North Korean involvement and added that such a development would be a "dangerous and highly concerning development" if true.
NATO Secretary General Mark Rutte said on Monday the dispatch of North Korean troops would significantly escalate the conflict.
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