The South Korean president, Park Geun-Hye, has ordered "airtight security" against the North after a flurry of propaganda and mixed messages from Pyongyang in the past week.
Park, who is at the end of a four-day state visit to India, told the country's defence minister and other security-related ministers to improve border security, according to a report published on Saturday by the Seoul-based Yonhap News Agency.
A presidential official told media in New Delhi: "In India, Park ordered the [South Korean] defence minister and other security-related ministers to make more efforts to keep an airtight security posture against [potential] provocations at a time North Korea is conducting a flurry of propaganda offensives."
Park's directive followed a surprise offer from Pyongyang on Friday, when it issued a statement calling for an end "all acts of provocation and slander", a day after it warned of "an unimaginable holocaust" if the South carried out military exercises with the US.
The olive branch was rejected by Seoul, with a government spokesman saying there was no intention of changing its behaviour or plans.