A 27-year-old South Korean soldier was killed and six others wounded Friday in an apparent shooting range accident during a military exercise near North Korean border.
An "unidentified explosion took place" during the front-line unit drill in Cheorwon, according to local news agency Yonhap.
The deceased was among a group of seven servicemen taken to a hospital, it said.
While an investigation is in progress, flames reportedly came from within one of the self-propelled howitzers being used for the exercise.
The incident punctuated ongoing tensions between the Koreas, as the North warned of a "catastrophe" if the South goes ahead with planned joint military drills with the United States next week.
U.S. President Donald Trump recently threatened Pyongyang with "fire and fury".
Seoul's Joint Chiefs of Staff announced Friday the annual Ulchi Freedom Guardian exercises -- bringing together tens of thousands of troops from both sides -- will go ahead Monday and continue until the end of the month.
South Korean President Moon Jae-in vowed a day earlier not to take any military action against the North, but Pyongyang has long viewed Seoul's military alliance with the U.S. as a threat.
North Korea has also so far refused to accept Moon's offers of dialogue since he took office in May.
The North's ruling party newspaper Rodong Sinmun insisted Friday that Seoul needs to break its ties with Washington if it "wants better relations with us".
Nearly 30,000 American military personnel are permanently stationed on the Korean Peninsula as a legacy of the 1950-53 Korean War -- a conflict that closed with a stalemate rather than a peace treaty.
