Zelensky said at a Thursday press conference at NATO headquarters in Brussels, Belgium, that North Korea was “preparing” to send 10,000 soldiers to fight in Ukraine.
“But they didn’t move them to Ukraine or to Russia" yet, Zelensky said.
South Korea's spy agency said Friday that North Korea was preparing to send around 12,000 troops to Ukraine, according to the country's news reports.
Zelensky and South Korea have both previously said that at least a small number of North Korean officers were operating in Ukraine.
But the numbers they claimed this week were preparing to deploy would be a significantly higher amount of forces.
NATO Secretary-General Mark Rutte, who appeared at the press conference with Zelensky on Thursday, said the Western security alliance was "very worried" about North Korean support for Russia.
"We have no evidence that North Korean soldiers are involved in the fight,” he added.
The Biden administration has also not confirmed that North Korean soldiers are fighting in Ukraine.
North Korea has long supplied artillery shells and short-range ballistic missiles to Russia in return for access to critical technology.
The alliance deepened earlier this year when Russian President Vladimir Putin traveled to North Korea and met with leader Kim Jong Un.
The two established a mutual defense treaty to come to each other's aid in the event of an armed attack on their respective soils.
Sending troops directly into Ukraine could have widespread ramifications for North Korea and would deepen Russia's reliance on other countries, including Iran and China, for Moscow to stay in the fight.
"If it's true, then to my mind it shows a level of desperation," said U.K. Prime Minister Keir Starmer in a Friday press conference.
