SEOUL, South Korea -- South Korea’s military fired warning shots, scrambled fighter jets and flew surveillance assets across the heavily fortified border with North Korea on Monday, after North Korean drones violated its airspace for the first time in five years in a fresh escalation of tensions.South Korea’s military detected five drones from North Korea crossing the border, and one traveled as far as the northern part of the South Korean capital region, which is about an hour’s drive away, South Korea’s Joint Chiefs of Staff said.North Korea had earlier released low-resolution photos of South Korean cities as viewed from space, but some experts in South Korea said the images were too crude for surveillance purposes.Such assessments infuriated North Korea, with Kim’s powerful sister Kim Yo Jong issuing a series of derisive terms to insult unidentified South Korean experts and express her anger.North Korea would eventually use its boosted nuclear capability as a bargaining chip to win international recognition as a legitimate nuclear state, the relaxing of international sanctions and other concessions, analysts say."