Referenews

South Korea’s military failed to shoot down any of the drones that flew over South Korean cities, including Seoul. Though larger combat drones that pose a real threat can be detected more easily, surveillance drones smaller than 10 feet are too small to easily intercept, South Korea’s military said. The military added that it didn’t aggressively engage with the North Korean drones out of concern for civilian safety and said it would improve its antidrone capabilities.

“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,” Mr. Yoon told a cabinet meeting Tuesday.

Last year, North Korean leader

Kim Jong Un

said the country would develop reconnaissance drones capable of flying up to 310 miles. One of the drones flown Monday traveled at about 62 miles an hour, at an altitude of about 1.8 miles, according to Seoul’s military. North Korean state media didn’t report Monday’s drone activity.

North Korea has about 300 drones, including those for reconnaissance, target practice and combat, according to a 2016 United Nations report. Drones recovered in South Korea showed some parts were imported from China, Japan and the U.S. Devices retrieved in South Korea in the past contained images of South Korean military facilities.

Mr. Yoon blamed predecessor

Moon Jae

-in for the lack of military preparedness stemming from his North Korea policy relying on Pyongyang’s good intentions and a 2018 military pact banning hostile activities in the border areas. Mr. Yoon’s ruling party has criticized North Korea for repeatedly violating the military agreement.

Mr. Yoon said he would expedite establishing a drone unit to monitor North Korean military facilities and and vowed to boost surveillance capabilities. Monday’s incident was the first time a North Korean drone had entered South Korean airspace since 2017. The size of the drones Monday were similar to a spy drone that crashed on a mountain in 2017, but the military was unable to determine if they were more technically advanced.

Some analysts say the drones are too small to conduct meaningful reconnaissance missions or conduct major attacks. But the drones would be capable of disrupting aviation activity.

The size of the drones seen Monday indicates they are too small to thoroughly capture South Korean facilities or carry bombs, said Cha Du-hyeogn, a former presidential security adviser.

“We don’t need to overreact and ignite fears of a security vacuum, but there is a need to advance capabilities to detect smaller drones and show any North Korean intrusion can be dealt with,” Mr. Cha said.

South Korean cities near the border have been on high alert since the Monday incident. On Tuesday, local media reported that there had been another possible drone sighting, but the Defense Ministry later said it was a flock of birds. Seoul’s military said it was unclear what facilities Monday’s drones might have captured, but it denied reports that a drone had flown over the presidential office.

Earlier this month, Pyongyang claimed to have conducted tests needed to develop a spy satellite, raising concerns that the Kim regime is advancing its technology to monitor South Korea.

“The psychological impact of the inability to detect and shoot down North Korean drones is concerning, because it incurs distrust for citizens,” said Yang Moo-jin, a professor at the University of North Korean studies in Seoul.

Write to Dasl Yoon at dasl.yoon@wsj.com