South Korean President Yoon Suk-yeol said on Tuesday he would advance the creation of a military unit specializing in drones, criticizing the military response to a border intrusion by North Korean drones. Five North Korean drones crossed into South Korea on Monday, prompting Seoul to scramble fighter jets and attack helicopters, and try to shoot them down, in the first such intrusion since 2017. The incident rekindled questions about South Korea's air defenses at a time when it is trying to rein in the North's evolving nuclear and missile threats. The military fired warning shots and some 100 rounds from a helicopter equipped with a machine gun, but failed to bring down any of the drones while they flew over several South Korean cities, including the capital, Seoul, for about five hours. "The incident showed a substantial lack of our military's preparedness and training for the past several years, and clearly confirmed the need for more intense readiness and training," Yoon told a cabinet meeting. Yoon blamed the unpreparedness for his predecessor's "dangerous" North Korea policy, which relied on Pyongyang's "good intentions" and a 2018 inter-Korean military pact banning hostile activities in the border areas. "We have been planning to establish a drone unit to monitor and reconnoiter major North Korean military facilities, and will now expedite the plan as much as possible," he added, vowing to boost its surveillance and reconnaissance capability with cutting-edge stealthy drones. The military said it chased one of the five drones over the greater Seoul area, but could not aggressively attack it because of concerns over civilian safety. "We operated detecting, tracking and shooting assets but there were areas where there might be civilian damage," an official at the Joint Chiefs of Staff (JCS) told a briefing on Tuesday. "So there were difficulties in actually carrying out operations." The incident was the latest airspace intrusion by unmanned aerial vehicles from the isolated North, with the two Koreas remaining technically at war after their 1950-53 war ended in an armistice, not a peace treaty. In 2017, a North Korean drone believed to be on a spy mission crashed and was found on a mountain near the border. In 2014, a North Korean drone was discovered on a South Korean border island. Those devices were deemed crude, mounted with cameras. The JCS said the latest drones were small, measuring about two meters (79 inches), but it was unclear whether they are more technically advanced. North Korean leader Kim Jong Un has publicly shown interest in drones, and pledged at a meeting of the ruling Workers' Party last year to develop new reconnaissance drones capable of flying up to 500 km (311 miles).