A North Korean shell has reportedly landed in South Korean territory. The incident prompted the South's military to respond with rifle fire, according to the defense ministry in Seoul.
For the second time in less than a week, North and South Korea's militaries traded fire near the border town of Yeoncheon.
On Friday, activists from the South launched balloons which had been carrying tens of thousands of leaflets denouncing the dictatorship in Pyongyang, according to South Korea's Yonhap news agency.
"There was an exchange of fire," an official at the Joint Chiefs of Staff office confirmed.
Northern forces shot at the South first, which then retaliated with rifle fire, Reuters news agency reported, citing the South Korean defense ministry.
There were no reports of damage or injury.
The incident coincided with worldwide media coverage of the notable absence of dictator Kim Jong Un from the North's 69th anniversary of the founding of the Worker's Party. His disappearance from the public eye in early September has fueled rumors about his health and his grasp on power.
Tensions have remained high over the past year between Pyongyang and Seoul in light of repeated threats of attack by northern dictator Kim Jong Un and the nearly six-month closure of the joint industrial park Kaesong.
However, relations appeared to be improving over the weekend when North Korean officials agreed to resume high-level dialogue with Seoul during a surprise visit to their southern neighbor.
Earlier this week, a North Korean navy vessel sailed into southern territory in the Yellow Sea near the island of Yeonpyeong.
Both sides exchanged warning shots and the North Koreans retreated to their own waters within 10 minutes.
The Yellow Sea maritime border was drawn by the United Nations at the end of the Korean War in the early 1950s without the North's consent. Pyongyang still rejects the line's validity.
While the Korean War ended over half a century ago, the neighboring countries technically remain at war because they signed an armistice, not a peace treaty.
kms/es (AP, AFP, Reuters)