N.Korea training 10,000 troops to help Russia in Ukraine: Zelensky

"They are preparing on their land, 10,000 soldiers, but they didn't move them already to Ukraine or to Russia," Zelensky said after meeting NATO defence ministers.

He made the claim about the 10,000 North Korean soldiers earlier Thursday after meeting EU leaders in Brussels -- without initially making clear where they were being trained.

Speaking alongside NATO chief Mark Rutte, Zelensky said there were already an unspecified number of "tactical personnel" and "officers" from North Korea in "occupied" Ukrainian territory held by Russia.

Rutte told their press conference that the alliance had "no evidence that North Korean soldiers are involved in the fight, but we do know that North Korea is supporting Russia".

Western officials said they were treating the reports with caution at this stage.

"We are tracking the possible deployment of North Korean troops to Russia," one official told reporters.

"North Korea has for quite some time now provided significant artillery munitions to Russia to support the war. And this is a new body of reporting that we're tracking."

The official said the reports concerned between 2,000 and 12,000 North Koreans but that -- if verified -- "it's probably towards the lower number".

"In terms of the veracity, it is a little bit too early to tell, to get some ground truth behind actually what is happening here," the official said.

Zelensky earlier qualified North Korea's move as "the first step to a world war", noting that Iran was also backing Russia with "drones and missiles", a claim that Tehran has repeatedly denied.

He said Russian President Vladimir Putin was "counting" on the North Korean soldiers because he was "afraid of mobilisation".

Zelensky held talks with EU leaders and NATO ministers to press for support for his "victory plan" to end the war against Russia.

He conducted a whirlwind tour of Western capitals earlier this month including Washington, Paris, Berlin, Rome and London to promote his initiative.

Experts have long said North Korean missiles are being deployed in Ukraine by Russian forces. Moscow and Pyongyang have denied this.

Putin made a rare visit to Pyongyang in June, when he signed a mutual defence agreement with leader Kim Jong Un.

Officials also claim Pyongyang has sent thousands of containers of weapons to Russia for use in Ukraine.

Moscow and Pyongyang have been allies since North Korea's founding after World War II and have become closer since Russia's 2022 invasion of Ukraine.