South Korea warned North Korea of stern punishment Wednesday should it carry out provocations in protest of anti-Pyongyang leaflet campaigns by civic groups here.

North Korea has demanded that the South deter its civic groups from releasing balloons carrying leaflets that criticize the North Korean regime, while the Seoul government has been cautious, citing their freedom of speech.

"If North Korea provokes, using the leaflet campaigns as an excuse, our military will, as warned repeatedly, mercilessly punish not only the origin of the provocations but also forces supporting it and its commanders," the defense ministry said in a brief release.

The warning came after the local daily Donga Ilbo reported, citing the leader of an abductee advocacy group in Seoul, that the North Korean military has completed drills to devastate South Korean border regions where civic groups release propaganda balloons. Choi said he learned of the tips from sources inside the communist country.

But the defense ministry here said the authorities do not have such intelligence and no signs have been detected of the North's such military drills.

"North Korea's artillery units have beefed up attack drills targeting our major facilities every year ... Though they are regular exercises, we are monitoring their activities along the border very closely," said a military officer here, requesting anonymity.

The civic groups, with most of their members being North Korean defectors, regularly send leaflets to their communist homeland to encourage their countrymen to rise up against the totalitarian regime.

Whether to regulate the campaigns has also been a hot-button issue in South Korea, as supporters claim it is a matter of freedom of expression while critics and residents in border regions say it could invite unnecessary trouble.

In October, the two Koreas exchanged machine gun fire across the border after the North apparently tried to shoot down balloons carrying anti-Pyongyang leaflets. (Yonhap)