The two Koreas exchanged machine gun fire Friday after the North launched shots toward balloons carrying anti-Pyongyang propaganda leaflets floated by South Korean civic activists, the Joint Chiefs of Staff said.

Some of the North Korean shots landed south of the border and the South fired back. No casualties were reported.

Joint Chiefs of Staff officials said shots could be heard from north of the border at around 3:55 p.m., about two hours after a group of South Korean activists flew 200,000 leaflets in balloons in a border village of Paju.

The officials added that shots apparently fired by anti-aircraft machine guns were discovered south of the border around 4:50 p.m. There were no reports of South Korean casualties, they said.

South Korea's military fired back about 40 rounds from its K-6 machine gun 10 minutes after issuing a warning message at 5:30 p.m.

Friday was the 69th anniversary of the founding of North Korea's ruling Workers' Party of Korea.

Pyongyang had warned through its official Korean Central News Agency on Thursday that Seoul would face "uncontrollable catastrophe" unless the leaflet campaign is stopped.

North Korean leader Kim Jong-un missed the crucial event extending a month-long absence and fuelling further speculation about his physical health and political future.

Kim, believed to be in his early 30s has not been seen since Sept. 3 when he attended a music concert with his wife in Pyongyang.

(From news reports)