The Democratic People's Republic of Korea (DPRK) sent troops to clear mines in Russia's Kursk region this year during its conflict with Ukraine, leader Kim Jong-un said in a speech carried on Saturday by state media in a rare acknowledgement by Pyongyang of the deadly tasks assigned to its soldiers.

Hailing the return of an engineering regiment, he noted that they wrote "letters to their hometowns and villages at breaks of the mine-clearing hours", according to the Korean Central News Agency.

The regiment suffered the "heartrending loss of nine lives" during the 120-day deployment that started in August, Kim said in a speech at a welcome ceremony on Friday, the agency reported.

He awarded the deceased soldiers state honours to "add eternal lustre" to their bravery.

"All of you, both officers and soldiers, displayed mass heroism overcoming unimaginable mental and physical burdens almost every day," Kim said.

The troops had been able to "work a miracle of turning a vast area of danger zone into a safe and secure one in a matter of less than three months".

Pyongyang confirmed in April that it had deployed troops to support Russia and that its soldiers had been killed in combat.

Images released by the agency showed a smiling Kim embracing returned soldiers, some in wheelchairs, at the grand ceremony in Pyongyang on Friday. (AFP)