A suspected landmine explosion rocked the heavily-fortified demilitarised zone (DMZ) between South Korea and North Korea.
At least two South Korean troops were injured in the blast, which took place on the southern side of the tense frontier.
The South Korean military said, according to Yonhap news agency, the two soldiers sustained wounds in their legs but were not in critical condition.
"There's no possibility of North Korea's involvement," a military official was quoted as saying.
The DMZ is one of the world's most heavily-armed border regions with the presence of nearly two million troops.