A plan to send balloons carrying propaganda leaflets into North Korea was cancelled on Monday after South Korean troops sealed off the site where the launch was due to take place.
Police said the decision was for security reasons.
On Friday, North Korea threatened military action if the propaganda drop by a group of defectors went ahead.
The BBC reports leaflets have been sent on many occasions in the past, but specific threats of retaliation such as the one on Friday are rare.
South Korea's Unification Ministry called for restraint from both sides.
