The sister of North Korean leader Kim Jong-un has warned that South Korea will face unspecified "new counteraction" by the North if it keeps sending anti-Pyongyang propaganda leaflets and playing its loudspeaker broadcasts across the border.

The statement by Kim Yo-jong came after the South resumed propaganda loudspeaker broadcasts toward the North for the first time in six years, in retaliation against the North's repeated sending of trash-carrying balloons, reports Yonhap news agency.

"If the ROK simultaneously carries out the leaflet scattering and loudspeaker broadcasting provocation over the border, it will undoubtedly witness the new counteraction of the DPRK," Kim said in the English statement carried by the Korean Central News Agency on Sunday, using the acronyms for the official names of the South and the North.

Kim claimed that the North had sent some 7.5 tonnes of "waste paper" in 1,400 balloons across the border over the weekend, arguing that they were just garbage that contained nothing related to political propaganda, unlike anti-Pyongyang leaflets sent by North Korean defectors in the South.

"It is quite different from the provocative political agitation rubbish scattered by the scum of the ROK against the DPRK," Kim said, adding that the South "will suffer a bitter embarrassment of picking up waste paper without rest, and it will be its daily work."

Kim claimed that the North had planned to stop sending balloons, but the "situation has changed" as the South resumed loudspeaker broadcasting across the border.

"I sternly warn Seoul to stop at once the dangerous act of bringing the further confrontation crisis and discipline itself," she said.

Seoul's unification ministry said that the government will not permit any attempts by North Korea to incite anxiety and confusion within South Korean society.

"North Korea should not make the mistake of using our rightful response as an excuse for provocation," said Koo Byoung-sam, the ministry spokesperson, during a press briefing.