In the end, anti-Pyongyang activists were successful in sending some of their propaganda leaflets northward.
Free North Korea Radio said on its website Monday evening that defector groups flew some 120-thousand leaflets from South Korea's western city of Incheon at 6 p.m., Korea time.
The launch came hours after the groups' original plan to fly some 200-thousand leaflets was thwarted by the South Korean government.
Local police blocked two entry ways to the South's border park of Imjingak, north of Seoul, all morning, where defector organizations had announced they would launch balloons carrying propaganda leaflets criticizing the hereditary succession in Pyongyang.
Some 80 North Korean defectors attempted to make their way through the barricade, but only managed to throw a small portion of the leaflets to the press at the scene.
The South Korean military and police reportedly obstructed the launch early Monday to avoid risking a security threat from north of the border.
North Korea last Friday threatened a merciless military strike, if any sign of a leaflet launch was detected.
Criticizing Pyongyang's threats, the Unification Ministry in Seoul, did however say that it has repeatedly urged the groups to refrain from provoking the North.
[Interview : Kim Hyung-suk, Spokesperson
Ministry of Unification] "Considering various situations, including the current inter-Korean relations, we have been asking the respective group for restraint. And we have once again requested them to exercise restraint this time."
The South Korean military says it will remain on high alert until Pyongyang suspends its combat readiness.
Over the weekend, the South's Defense Minister Kim Kwan-jin ordered a complete retaliation, should North Korea conduct a provocation in the future.
Kim Han-ul, Arirang News.
Activists floated the propaganda leaflets into the North from Ganghwa Island near Incheon on Monday evening.
According to one of the organizers the leaflets criticized the hereditary power transfer of Kim Jong-il to Kim Jong-un.