Soldiers fighting for Ukraine describe facing relentless waves of determined North Korean troops, Russian units with improved tactics, and Ukraine’s own struggles with exhaustion and sinking morale.

North Korea has not responded to reports of its troops captured or killed by Ukraine forces. It has never publicised the deployment or large shipments of North Korean artillery shells and other weapons sent to Russia to help its war against Ukraine, although they marked the country’s first intervention in a major armed conflict overseas in decades.

South Korea's military said on Friday that it suspects North Korea is preparing to send more troops to Russia to fight Ukrainian forces, even after suffering losses and seeing some of its soldiers captured.

Ukraine President Volodymyr Zelenskyy said this month that as many as 4,000 North Korean troops have been killed or wounded in recent weeks, with only two captured alive. Both men were wounded and transferred to custody in Kyiv, where Zelenskyy said they are being interrogated and treated for their injuries.

British intelligence has reported that one-third of the troops deployed alongside Russian forces in Ukraine are already out of action. Pyongyang sent a contingent of 12,000 soldiers to Russia to assist local forces in regaining lost territory in the Kursk region,