Pyongyang regularly criticizes such drills as rehearsals for invasion and sometimes responds with weapons tests, but Seoul and Washington say they are purely defensive.

Kim said the "security environment" around North Korea is "getting more serious day by day" and "requires us to make a radical and swift change in the existing military theory and practice and rapid expansion of nuclearization," the official Rodong Sinmun newspaper reported, paraphrasing his remarks.

SEOUL, South Korea (AP) — North Korean leader Kim Jong Un condemned South Korean-U.S. military drills and vowed a rapid expansion of his nuclear forces to counter rivals, state media said Tuesday, as he inspected his most advanced warship being fitted with nuclear-capable systems.