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

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.

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.