On Thursday, two KF-16 fighter jets dropped eight 500-pound MK-82 bombs outside a training range in Pocheon, some 40 kilometres north of Seoul, during live-fire drills, injuring 31 people, including 19 civilians.

The Air Force had earlier said pilot error was the suspected cause of the accidental bombing as one of the pilots had entered the wrong target coordinates prior to takeoff.

Releasing the interim findings, the Air Force said the target's latitude coordinates were incorrectly entered after the pilot of the first jet read them aloud for the second pilot to input into the computer system during preparations.

It currently remains unclear if the coordinates were misread or misheard, but the Air Force said there were still at least three opportunities to catch the mistake and prevent the accidental bombing.

"The pilot of the first aircraft should have double-checked the target at least three times throughout the process of the assignment but did not do so," it said in a statement.

The pilot was mandated to confirm the target when entering the coordinates in the joint mission planning system computer and checking the aircraft once a data transfer cartridge has been fitted on the aircraft ahead of takeoff, according to the armed service.

After takeoff, the pilot perceived the flight route to be slightly different compared with a preparatory training course but went ahead with the bombing, without verifying the coordinates, in order to meet the target time, it added.

Meanwhile, the second pilot separately entered the correct coordinates for his jet but still proceeded with the bombing following the first jet's lead as the training was designed as a simultaneous strike drill.

The Air Force also attributed the accident to inadequate management and inspection procedures, saying specific instructions were not given to the pilot by superiors.

Meanwhile, it found that the Master Control and Reporting Center in charge of aircraft flight activities and the Joint Terminal Attack Controller that directs air strikes on the ground followed proper procedures.

The troops on the ground gave final approval for the bombing after the pilot notified them that he had visually confirmed the target, even though he had not due to time constraints, according to the Air Force.

As part of preventive measures, the Air Force vowed to strengthen procedures to confirm target coordinates in live-fire drills and overhaul its overall reporting system for abnormal situations.

The armed service also announced plans to bolster the inspection of missions and strengthen safety training on live-fire drills for all pilots.

"The Air Force, which should protect the lives and property of the people, inflicted harm on the people," Air Force Chief of Staff Gen. Lee Young-su said in a public apology.

"It was an accident that should never have happened and one that should not recur."

The Defence Ministry said it plans to conduct its own probe into the bombing, considering the gravity of the accident.

Authorities are expected to investigate the two pilots in question, as well as others who were involved in the training. They could face criminal charges based on the investigation results.

The Air Force, which had grounded nearly all aircraft after the accidental bombing, said it plans to resume flight training in phases Monday, in conjunction with the beginning of a major springtime joint exercise between South Korea and the United States, Yonhap news agency reported.

Still, live-fire drills will only resume once preventive measures are established and relevant measures are completed, it added.