Ukraine has been hit by a surge in Russian ballistic missile attacks, about a third of which used North Korean weapons that can only fly because they run on Western circuitry, obtained despite sanctions,

Russia reportedly provided North Korea with oil, anti-air missiles and economic help in exchange for troops to support Moscow's war on Ukraine.

Around 10,900 North Korean troops have been deployed to Kursk as part of Russia's airborne unit and marines, with some already participating in battles in the Ukraine war, a South Korean lawmaker said on Wednesday,

Pyongyang has long coveted an advanced air-defense system to guard against missiles and war planes from the United States and South Korea.

The U.S., South Korea and others say North Korea has sent more than 10,000 troops to Russia to support its war against Ukraine.

The South Korean assessment came after Russia warned Monday that President Joe Biden’s decision to let Ukraine strike targets inside Russia with U.S.-supplied longer-range missiles adds “fuel to the fire” of the war.

Russia provided North Korea with missiles in exchange for sending troops to Ukraine, according to a senior South Korean official.

The United States expects that thousands of North Korean troops massing in Russia will "soon" enter combat against Ukraine, Pentagon chief Lloyd Austin said Saturday. About 10,000 North Korean soldiers were believed to be based in the Russian border region of Kursk,