North Korea fired a shell toward South Korea on Thursday, an official with the South Korean Defense Ministry told CNN.
South Korea responded by firing a few dozen shells at the area from where the North Korean projectile was fired, the official said.
Tensions have spiked on the Korean Peninsula in recent weeks after two South Korean soldiers were seriously wounded by land mines in the demilitarized zone.
South Korea has accused the North of planting the mines, an allegation Pyongyang denies.