Ukrainian forces mounted a lightning incursion there in August, but Russia has since amassed thousands of troops in a counter-attack.
Zelensky said “several” North Korean soldiers were “seriously wounded and could not be resuscitated” during their capture, which suggests that some of them may have been killed by comrades.
He said these troops were being sent to fight with “minimal protection” and were suffering a “great deal” of losses, but Ukrainians have been unable to capture them as prisoners.
“Their own people are executing them,” he said.
Pyongyang has deployed an estimated 11,000 soldiers to the Kursk region to seize back territory taken by Ukraine over the summer, according to estimates by the US and its allies.
Western officials have claimed that a lack of training, unfamiliar terrain, and poor communication with Russian officers due to the language barrier has led to them sustaining heavy injuries and losses on the battlefield.