North Korea allegedly fired a rocket at South Korea, prompting the South's military to return "tens" of 155mm artillery rounds to the origin point of the projectile on Thursday.
The alleged North Korean missile landed in an area roughly 60 km north of Seoul in the western part of the border zone, the defense ministry said, according to Al Jazeera.
"Our military has stepped up monitoring and is closely watching North Korean military movements," the ministry said.
Tensions between the neighbors have increased dramatically in recent weeks since South Korea accused the North of planting mines in a demilitarized zone that wounded two South Korean soldiers, according to CNN.
A United Nations investigation concluded that the mines were laid by North Korea, but Pyongyang has denied the allegation.
Following the accusation, South Korea vowed a "harsh" response to the land mines and resumed its broadcasting of propaganda messages over the militarized border from huge sets of loudspeakers - an action it hasn't done in more than a decade, according to The Wall Street Journal.
In response to the broadcasting, which North Korea deemed a "direct action of declaring a war," the country threatened over the weekend to blow up the South Korean speakers and warned the South of "indiscriminate strikes."
According to the testimony of Seoul officials, North Korea allegedly made good on that promise, since the projectile in question targeted one of South Korea's loudspeakers at the border.
Coincidentally, South Korea has started its annual military exercises with the United States and other countries this week. North Korea considers the drills as a prelude to an invasion and threatened to attack both South Korea and the U.S. in response, as reported earlier by HNGN.
