After North Korean drones entered South Korean airspace, the military apologized for failing to defend itself. The armed forces are sorry they failed to shoot down the drones, Lt. Gen. Kang Shin Chul said. Warplanes and helicopters rose on Monday but failed to shoot down any of the invading North Korean drones.

The first “North Korean unmanned aerial vehicle” has been spotted around Gimpo airspace in Gyeonggi province, it said. A total of several drones had penetrated the country’s airspace. The aircraft then returned to North Korea or disappeared from South Korean radar.

Seoul had fired warning shots in response, and fighter jets and attack helicopters were also deployed.

The incident raised questions about the operational readiness of South Korea’s air defenses. The armed forces deployed fighter jets and helicopters again on Tuesday after suspicious flying objects were sighted near the border. Authorities sent out text messages informing citizens of more North Korean drones. But there was no danger: the flying objects turned out to be a flock of birds, as the military later announced.

South Korean President Yoon Suk Yeol announced the country would strengthen anti-aircraft defenses. The planned establishment of a drone unit to monitor military installations in North Korea will be accelerated, the president said during a cabinet meeting. “We will also introduce state-of-the-art stealth drones and strengthen our surveillance capabilities.”

It is the first time in five years that North Korean drones have entered South Korean airspace. The internationally isolated country has already tested numerous weapons this year. According to Seoul, Pyongyang fired two rockets last Friday.