NATO's dispatch of troops to North Korea and Russia "cannot be confirmed at this stage, but we are deeply concerned."

"At this stage, we cannot confirm the relevant reports, but it is clear that they are deeply concerning," he said in response to Ukraine's claim that NATO had provided personnel to North Korea's Russia.

NATO Secretary-General Mark Rutter responded to the questions at a press conference in Brussels, Belgium, on the afternoon of the 16th local time.

"Even if the dispatch is not true, North Korea is already supporting Russia's war with weapons," Rutter said.

On the same day, Ukrainian President Volodymyr Zelensky told Congress that his country's intelligence agency confirmed that North Korea had sent replacement personnel and military personnel for Russian factories.

Since the beginning of this month, local media in Ukraine have reported a series of rumors of dispatch.

But NATO appears to have remained cautious, refraining from commenting on whether it is true or not in line with the U.S. stance.

"We can't independently confirm (the facts) about that report," National Security Communications Adviser John Kirby said in a telephone briefing the day before when asked about the relevant report.