North Korean troops were killed fighting Ukrainian forces in the Russian border region of Kursk, the US said.
These would be the first reported victims since it showed up In October, North Korea sent around 10,000 soldiers to bolster Russia’s war efforts.
According to the Ukrainian military intelligence service GUR, at least 30 North Korean soldiers were killed or wounded in fighting over the weekend.
The BBC has not independently verified the claims.
The North Korean troops – none of whom have any combat experience – are believed to have spent the first few weeks after being deployed to Russia in training and then in support roles.
On Saturday, Ukrainian President Volodymyr Zelensky said the Russians had begun using “significant numbers” in their attacks on Kursk, part of which Ukraine has since occupied launch a surprise attack in August.
Speaking to reporters on Monday, Pentagon press secretary Maj. Gen. Pat Ryder said the U.S. believes North Korean soldiers “fought alongside Russian forces in Kursk” and “suffered both killed and wounded casualties.”
He did not give specific numbers but said troops had been fighting since “just over a week ago.”
He added that it appeared that the North Koreans were being deployed in infantry roles and that their involvement so far was believed to be limited to Kursk, meaning they had not been deployed to Ukraine itself.
Russian forces, which launched a full-scale invasion of Ukraine in February 2022, have advanced into eastern parts of the country in recent months.
The GUR said the North Korean victims occurred on Saturday and Sunday in the Kursk villages of Plehovo, Vorobzha and Martynovka.
On Monday, President Zelensky posted drone footage on Telegram that showed several men hiding behind trees and said they were North Korean troops who had just taken part in an attack on a Ukrainian position.
He also released footage that he said showed Russian troops trying to hide the presence of North Koreans on the battlefield by using a bonfire to burn the faces of those killed.
“Ukraine’s defense forces and intelligence agencies are working to determine the full extent of the actual losses suffered by Russian units, which include North Koreans,” he said.
He added that there was “not a single reason for North Koreans to die in this war.”
The Kremlin referred questions about North Korean deaths to the Russian Defense Ministry, which did not comment.