A top North Korean general was wounded in a recent Ukrainian strike in the Kursk region of Russia, The Wall Street Journal reported.
The Western official who spoke to the outlet did not indicate how the senior North Korean general was wounded or the extent of his injuries.
Earlier in November, the Pentagon confirmed that North Korea had deployed 10,000 troops to aid Russian President Vladimir Putin in his war against Ukraine. In June, the two countries signed a "comprehensive strategic partnership treaty," which ensures both nations will provide military assistance using "all means" if either is attacked.
Ukrainian President Volodymyr Zelenskyy confirmed last week that North Korean troops have engaged in direct combat with Ukrainian forces, resulting in several casualties.
"Some of these troops have already taken part in hostilities against the Ukrainian military. Yes, there are already losses, this is a fact," Zelenskyy said without specifying which side had suffered casualties.
On Tuesday, it was reported that Ukraine had targeted a Russian weapons arsenal using the long-range U.S.-made Army Tactical Missile System, known as ATACMS. The attack marked a major escalation on the 1,000th day of the war.
John Kirby, national security communications adviser said last month that any North Korean troops would be "fair game" for the Ukrainians.
"They're fair targets. And the Ukrainian military will defend themselves against North Korean soldiers the same way they're defending themselves against Russian soldiers.
"And so, the ... possibility that there could be dead and wounded North Korean soldiers fighting against Ukraine is ... absolutely real if they get deployed," Kirby added.