South Korea's Air Force on Thursday said one of its fighter jets had accidentally dropped eight bombs in the wrong place during a training exercise, resulting in civilians being injured.

"Eight MK-82 general-purpose bombs were abnormally released from an Air Force KF-16 aircraft, landing outside the designated firing range," the Air Force said, adding it deeply regretted the incident "which resulted in civilian casualties".

An official at Gyeonggi-do Bukbu Fire Services said out of the eight people who had been wounded, four were seriously hurt.

Pocheon is about 40 kilometres northeast of Seoul and near the heavily militarised border with North Korea.

Fire officials suspected the munitions dropped on the town was from ongoing live-fire joint military exercises conducted by South Korea and the United States, the official said.

Photographs shared by news agency News1 that it said were from the scene showed a badly damaged house with rubble strewn on the ground next to it.

South Korea's defence ministry was not immediately available for comment.

The ministry said earlier on Thursday that South Korea and US forces were holding their first joint live-fire exercises in Pocheon which were linked to annual military drills due to start next week. (Agencies)