One dead, six injured in South Korean artillery drill
The incident did not have anything to do with North Korea, said the official, who declined to be identified as he was not authorised to speak to the media.
The blast took place during a regular training session, the official added.
A military spokesman could not immediately be reached.
The neighbours technically remain at war, since the 1950-1953 Korean War concluded in a ceasefire.
The military authorities were quoted as saying the accident occurred at around 3:00p.m. local time (0600 GMT) at a gunnery range in Cheorwon, Gangwon province that borders the DPRK.
The seven soldiers suffering minor and serious injuries were taken to a nearby hospital, but one died while being treated.
The exact cause of the accident has yet to be identified. An investigation was underway.