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,

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.

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