The South Korean military estimates that North Korea spent some 550 million won, or around 408-thousand U.S. dollars, to carry out 22 trash balloon launches, saying that was enough to purchase over 970 tons of rice.

In policy briefing documents submitted for a parliamentary audit on Tuesday, the defense ministry said Pyongyang is sending the trash balloons as a low-cost, high-efficiency "gray zone" provocation.

The ministry said it believes the North is seeking to end anti-Pyongyang propaganda leafleting activities by defectors’ groups in the South by increasing the South Korean military's fatigue and by exacerbating discord within South Korean society.

It also said it believes Pyongyang continues to lay mines and build barriers along the Demilitarized Zone in accordance with a policy that views the two Koreas as hostile states.

Seoul said that by unveiling a uranium enrichment facility in September, the North appeared to be highlighting its status as a nuclear power in an attempt to increase its bargaining power with the U.S.