South Korea's military apologized on Tuesday for failing to shoot down five North Korean drones that crossed the inter-Korean border on Monday, after facing widespread criticism for its lack of preparation.

“Yesterday, five enemy drones invaded South Korean airspace, and our military detected and tracked them, but we apologize that we were unable to shoot them down,” the Joint Chiefs of Staff South said. -Korean (JCS) in a statement.

Monday's incursion prompted Seoul to fire warning shots and deploy fighter jets and helicopter gunships to bring down the drones, one of which had reached airspace near Seoul.

All the drones seem to have returned to the north despite a hunt that lasted five hours.

The JCS acknowledged that while the military can counter "attack drones that pose a real threat", there is a limit to their ability to detect and strike smaller spy drones.

"As a result, the military's lack of preparedness has caused a great deal of public concern," he added.

South Korean President Yoon Suk-yeol told a cabinet meeting on Tuesday that the incident showed the military's state of preparedness was "very insufficient".

Yoon ordered the acceleration of a project to launch a drone unit to carry out surveillance and reconnaissance operations of North Korea's main military installations. The plan calls for the introduction of advanced stealth drones.

The foray into South Korean airspace was the first in five years and comes after a series of weapons tests by Pyongyang.