The air assault came as most of the more than 10,000 North Korean troops sent by Pyongyang to help Moscow in the war are engaged in combat in Russia's Kursk border region, according to the Pentagon. A Ukrainian army incursion into Kursk three months ago has succeeded in holding a broad area of land and has embarrassed the Kremlin.

Secretary of State Antony Blinken says the Biden administration is determined in its final months to help Ukraine keep fighting.