Yonhap News Agency quoted South Korea's Defense Ministry on Monday saying that the leaflets were sent over the border in balloons in the past week by North Korea's military. Pyongyang also broadcast propaganda over loudspeakers, attacking South Korean President Park Geun-hye.

Most of the flyers were collected near the border in South Korea's Gyeonggi province, but some made it as far as Seoul.

Nuclear test

The broadcasts and the pamphlets appeared to be in response to South Korea's decision, earlier in January, to blast a mix of K-pop and propaganda messages into North Korea, also using giant banks of speakers on the heavily militarized border.

South Korea's propaganda broadcasts came in light of Pyongyang's fourth nuclear test, carried out on January 6. The international community condemned the test, with the US and Japan describing it as "yet another violation of [North Korea's] obligations and commitments under international law."

Psychological warfare

Seoul is now also considering installing giant electronic signboards on the North-South border to display messages and videos.

The escalating psychological warfare between the North and South dates back to the 1950-53 Korean War. Such leafleting by the North has been rare, however, since the two Korea's struck a tension-relieving deal last year, which saw the South cut the music and propaganda.

ksb/jm (AFP, AP, dpa)