South Korean activists were thwarted by egg-throwing protesters as they approached the border to launch balloons carrying leaflets into the North.
The activists planned to release balloons carrying about 40,000 leaflets criticising North Korea's government across the heavily-militarised frontier from a park in the border town of Paju.
"If a rash act of scattering leaflets slandering our dignity and system is taken again in South Korea, its consequences will be very grave."
Near the park, about 20 local residents set up a road block with two tractors, carrying a placard reading "Stop anti-North leaflet launch jeopardising our lives!"
"We will become the victims of shelling if leaflets are scattered," read another placard put up in a tree.
Al Jazeera's Harry Fawcett, reporting from Paju, said the activists were immediately pelted with eggs when they got off the bus that brought them to the town, about 40km north of Seoul.
"They were met with acrimonious style by residents here, who, just a couple of weeks ago, saw a military response from a similar anti-North Korean balloon launch," he said.
"The South Korean government has said it does not want this launch to go ahead, but under South Korean law it is powerless to prevent it. It seems it's being prevented by other means."
Hundreds of South Korean police were deployed near the border on Saturday before the proposed launch following threats of violent retaliation from Pyongyang.
Pyongyang, which refers to the activists as "human scum", has long condemned the launches and in recent weeks has stepped up its demands for Seoul to ban the practice entirely.
Two weeks ago, North Korea border guards attempted to shoot down some balloons, triggering a brief exchange of heavy machine gun fire between the two sides.
"If a rash act of scattering leaflets slandering our dignity and system is taken again in South Korea, its consequences will be very grave," Rodong Sinmun, the North's official newspaper, said in a commentary on Saturday.
The North has warned that failure to halt future launches could put at risk the planned resumption of high-level talks between the two Koreas.
Local residents in Paju insisted that the threats of military retaliation by North Korea are credible and that the activists are putting their lives and businesses at risk.
Source: Al Jazeera and agencies