Ukrainian forces captured two North Korean soldiers fighting alongside Russian troops in the Russian border region of Kursk, Ukrainian President Volodymyr Zelensky said on Saturday.

He commented a few days after Ukraine started making new attacks in Kursk to hold the ground won in a lightning invasion in August that resulted in the first occupation of Russian territory since World War II.

Moscow’s counterattack left Ukrainian forces stretched thin and demoralized, killing and wounding thousands and recapturing more than 40% of the 984 square kilometers (380 sq mi) of Kursk that Ukraine had captured.

“Our soldiers captured North Korean soldiers in Kursk. These are two soldiers who, although wounded, survived, were taken to Kiev and are communicating” with Ukrainian security services, Zelenskyy said in a post on the Telegram messaging app.

He shared photos of two men resting on beds in a room with barred windows. Both wore bandages, one around the jaw and the other around both hands and wrists.

Zelenskyy said capturing soldiers alive “was not easy”. He claimed that Russian and North Korean forces fighting in Kursk tried to cover up the presence of North Korean soldiers, including killing wounded comrades on the battlefield to avoid their capture and interrogation by Kiev.

The Ukrainian security service SBU provided more information about the two soldiers on Saturday. The statement said one had no documents, while the other carried a Russian military ID in the name of a man from Tuva, a Russian region bordering Mongolia.

“Prisoners do not speak Ukrainian, English or Russian, so communication with them takes place through Korean translators in cooperation with South Korean intelligence,” the statement said.

According to the SBU, one of the soldiers claimed he was told to go to Russia for training, not to fight against Ukraine.

The agency said both men had been given medical care in accordance with the Geneva Conventions and were being investigated “in cooperation with South Korean intelligence”.

AND a senior Ukrainian military official said last month that several hundred North Korean soldiers fighting alongside Russian forces at Kursk were killed or wounded in action.

The official provided the first significant estimate of North Korean casualties, which came weeks after Ukraine announced that Pyongyang had sent 10,000 to 12,000 troops to Russia to help it in its nearly three-year war against its much smaller neighbor.

The The White House and the Pentagon confirmed last month that North Korean forces were fighting on the front lines mostly in infantry positions. They are fighting with Russian units, and in some cases independently, around Kursk.