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 40km northeast of Seoul and near the heavily militarised border with North Korea.

Fire officials suspected that the shell dropped in the town was from ongoing live-fire joint military exercises conducted by South Korea and the US, the official said.

The official did not have further details about what type of shell it might be, but said fire authorities suspected a fighter jet might have misfired during the exercises.

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.