This photo released on Sunday shows a balloon containing South Korean snacks and other consumer goods. (KCNA)

The powerful sister of North Korean leader Kim Jong-un said Sunday that South Korea will have to pay a "dear price" for sending propaganda leaflets across the border the previous day.

Kim Yo-jong, vice department director of the central committee of the North's ruling Workers' Party, said "various kinds of political agitation leaflets and dirty things" were dropped by the South near the border and further inland.

"We strongly denounce the shameful and dirty acts of the ROK scum who committed the provocation of scattering anti-DPRK political and conspiratorial agitation things once again in disregard of our repeated warnings," she said in a statement carried by the North's Korean Central News Agency, referring to South and North Korea by their formal names, the Republic of Korea and the Democratic People's Republic of Korea.

"There will be no house owner who hardly gets enraged at such dirty rubbish scattered in the clean yard, which even a mutt dislikes to touch," she said.

North Korea has reacted angrily to South Korean activists sending balloons across the border carrying anti-Pyongyang propaganda leaflets and South Korean consumer goods.

Kim said North Korea's security forces have blocked off the areas where the leaflets were found and are carrying out disposal work.

"There is a limit to patience," she said. "The DPRK people's anger at the most disgusting curs has reached the extremes. The scum will have to pay a dear price." (Yonhap)