US Defense Secretary Lloyd Austin has confirmed that North Korean troops are in Russia, marking the first official acknowledgment of this development.

During a press conference on Wednesday, Austin told reporters, “There is evidence that there are DPRK troops in Russia.” The acknowledgment follows previous warnings from Ukraine and South Korea about North Korea’s involvement in the war. Ukrainian President Volodymyr Zelensky previously warned that 10,000 North Korean troops were being prepared to assist Russia in its war against Ukraine, according to Axios.

Similarly, South Korea expressed concern on Tuesday, warning that it may consider supplying weapons to Ukraine out of fear that Russia will provide North Korea with more sophisticated weaponry in return for their assistance. In June, Russia and North Korea signed a mutual defense partnership.

Both Russia and North Korea have denied reports of North Korean troops being deployed. However, National Security Council spokesman John Kirby provided further details on Wednesday, estimating that at least 3,000 North Korean troops have already arrived in Russia.

“We assess that between early- to mid-October, North Korea moved at least 3,000 soldiers into eastern Russia,” Kirby said. “We assess that these soldiers traveled by ship from the Wonsan area in North Korea to Vladivostok, Russia. … We do not yet know whether these soldiers will enter into combat alongside the Russian military, but this is certainly a highly concerning probability. After completing training, these soldiers could travel to western Russia and then engage in combat against the Ukrainian military.”

At this point, the US does not believe that North Korean troops have reached Ukraine. However, their movement has raised concerns about escalating the conflict. Austin stated that the US is still working to determine what role these troops will play, CNN reported.

"If they're co-belligerents, if their intention is to participate in this war on Russia's behalf, that is a very, very serious issue," Austin suggested. He also noted that the deployment of North Korean troops indicates that Russian President Vladimir Putin "may be even in more trouble than most people realize.”