North Korean leader Kim Jong-un said he sent troops to help Russia's military agreement with Moscow "annihilation" of Ukrainian troops.

North Korea confirmed for the first time that it sent troops to Russia to support Moscow's war against Ukraine, whose troops would help regain Russian territory occupied by the Ukrainian military in the Kursk region.

In a statement provided to North Korea's Central News Agency (KCNA), the Central Military Commission of the ruling Workers' Party said the country's leader Kim Jong Un had sent troops to fight along with Russian troops as part of a joint defense treaty between Moscow and Ponwan.

KCNA quoted Kim as saying that the soldiers were deployed to "annihilate and eliminate the Ukrainian neo-Nazi occupiers and cooperate with the Russian armed forces to liberate the Kursk region."

"Those who fight for justice are heroes and representatives of the honor of the motherland," KCNA quoted Kim as saying.

North Korea "sees it as an honor to form an alliance with a powerful country like the Russian Federation."

Russian Presidents Vladimir Putin and Kim signed a comprehensive strategic partnership treaty last June, where the two countries helped each other militarily when the war broke out.

According to South Korea's official Yonhap News Agency, Kim also said a monument will be built in the capital Pyongyang to honor those who fought against Ukraine.

"The flowers that pray for immortality will be placed before the tombstones of the fallen soldiers, effectively acknowledging the troops who died in the battle," Yonhap reported.

Ukrainian officials said earlier this year that about 14,000 North Koreans targeted their troops, including 3,000 reinforcements, were sent to replace the early battlefield losses of the North Koreans.

It was reported that the North Koreans lacked armored vehicles and were not familiar with drone warfare. They suffered heavy casualties early in the battle, but quickly adapted and later made contributions to help restore Russia's Kursk region from the occupied Ukrainian army.

It is estimated that the casualties of North Korean troops fighting for Russia vary greatly.

South Korea's National Intelligence Agency (NIS) said in January that about 300 North Korean soldiers were killed and another 2,700 were injured in the fight.

Ukrainian President Volodymyr Zelenskyy set the number of North Koreans killed or injured at 4,000, while the United States estimates a lower number of around 1,200 casualties.

North Korea's statement came after Russian Chief of Staff Valery Gerasimov welcomed the "heroism" of North Korean soldiers on Saturday, saying "significant help was provided for defeating the Ukrainian armed forces", while reporting to Putin that Kursk had recovered from Ukrainian forces.

Ukraine's General Staff quickly refuted, saying that its defensive operations in certain areas of Kursk are still continuing.

North Korea and other "third countries" have "permanently" Russia's war against Ukraine, it must end and Moscow's support for Pyongyang should end, the U.S. State Department said in a statement on Sunday night.