North Korean troops in Russia shelled by Ukrainians: Official

North Korean troops have been fired upon for the first time since sending thousands of soldiers to fight alongside Russians against Ukraine, according to a Ukrainian official.

Andrii Kovalenko, Ukraine's head of the Center for Countering Disinformation at the National Security and Defense Council, said in a Monday post on Telegram that the first North Koreans have come under fire in Russia's Kursk region but did not provide any other details.

In another post, Kovalenko said North Korean troops are wearing Russian uniforms and are being trained to use drones, while Russia plans to send trainers to Pyongyang to directly instruct its ally on operating unmanned aircraft systems.

Ukrainian President Volodymyr Zelensky said in a Monday night video address that 11,000 North Korean troops are in Kursk.

"We are seeing an increase in North Koreans but unfortunately, not an increase in our partners' response," he said.

Pentagon press secretary Maj. Gen. Pat Ryder told reporters Monday that at least 10,000 North Korean troops were in Kursk, a region of Russia bordering Ukraine's Sumy province and which Ukrainians have held for nearly three months.

Ryder said that the number of North Koreans in Russia could be as high as 12,000 and could also increase.

He added that the U.S. expects the North Koreans to provide some type of combat ability to Russia, though their role was not yet clear, and warned that "should these troops engage in combat support operations against Ukraine, they would become legitimate military targets."

"We would fully expect that the Ukrainians would do what they need to do to defend themselves and their personnel," Ryder said.

Ukraine first claimed that North Korean troops were deployed to assist Russia in mid-October, a fact that was later confirmed by the U.S. and NATO later that month.

Zelensky has since pleaded for western allies to step up the response to the increasing Russia-North Korea partnership, which also includes Pyongyang supplying artillery shells and short-range ballistic missiles in return for access to critical technology and other aid.