(CNN) -- The South Korean military accidentally fired a shell during a land-based military exercise Sunday afternoon, a South Korean military spokesman told CNN.

The country's defense ministry declined to provide details about the land exercise.

The United States and South Korea also began naval drills in the Yellow Sea Sunday, but a U.S. military spokesman has said no live firing will take place during those exercises.

The shell was fired by a unit located near Munsan, South Korea, and landed on the southern side of the military demarcation line, the South Korean officer said.

"The South notified North Korea that this was accidental firing through a statement issued by the chief delegate of inter-Korean general level talks," the officer said. He added, "the military is looking into the cause of the accident."

North Korea has not responded to the incident, according to the South Korean media officer.