The accident occurred Thursday near the North Korea border, where U.S. and South Korean forces were conducting a live-fire drill in preparation for annual joint exercises.
The South Korean military said the accident near the North Korean border occurred during training ahead of Freedom Shield, an annual U.S.-South Korea joint military exercise.
The number of people injured after South Korean fighter jets accidentally dropped bombs on a civilian area on Thursday increased to 15 civilians and 14 soldiers, the country's defence ministry said.