The White House and Pentagon have put Russia and North Korea on notice, following several international reports alleging that North Korea has sent troops to fight alongside Russian forces in Ukraine.

"If they are co-belligerents, if their intention is to participate in this war on Russia’s behalf, that is a very, very serious issue," US Defense Secretary Lloyd Austin said while returning from his fourth visit to Kiev, where he announced the latest $400 million arms package.

White House: John Kirby 

Starting last week, South Korean intelligence backed claims by President Zelensky which said at least 10,000 North Korean troops are mustering in Russia to deploy in Ukraine. Seoul also claimed that 1,500 DPRK are already in Ukraine's east.

White House national security spokesman John Kirby on Wednesday described that the US assesses that at least 3,000 North Korean soldiers arrived at Russia's Pacific port of Vladivostok. They reportedly arrived by boat earlier this month.

"These soldiers then travelled onward to multiple Russian military training sites in eastern Russia, where they are currently undergoing training," Kirby said.

"We do not yet know whether these soldiers will enter into combat alongside the Russian military, but this is certainly a highly concerning probability," he continued. And that's when he added the warning and threat:

...should they deploy to fight against Ukraine, "they’re fair game".

Yonhap News Agency had previously reported that the country's main intelligence agency, NIS, assessed that Pyongyang has made the decision to deploy four brigades to Ukraine, which amounts to an estimated 12,000 troops.

In a Tuesday evening address, President Zelensky echoed this figure, saying: "We have information that two units of military personnel from North Korea are being trained – potentially even two brigades of 6,000 people each."

Zelensky has further commented that this is a sign of the war's growing internationalization in Moscow's favor. He has demanded that his Western backers respond.

In an interview Alexander Lukashenko, leader of Belarus, tells me that North Korean troops fighting alongside Russia in Ukraine “would be a step towards an escalation of the conflict.” Producer @LizaShuvalova @BBCNews pic.twitter.com/dNYrUo1KSl

— Steve Rosenberg (@BBCSteveR) October 24, 2024

Already, Pyongyang has long faced accusations that it is shipping weapons, and especially artillery shells, to Russian forces for use in Ukraine.

Kiev has spoken of an 'axis' which is at war against Ukraine, including Russian, Iran, and now North Korea.