North Korean leader Kim Jong Un's sister has rebutted South Korea's claims that Pyongyang removed some of its propaganda-blasting loudspeakers along the border.

North Korea has "never removed" the speakers and "are not willing to remove them", Kim Yo Jong said in a statement published by state media KCNA on Thursday.

"We have clarified on several occasions that we have no will to improve relations with [South Korea]," she said, adding that this stance "will be fixed in our constitution in the future".

South Korea's military said earlier this week that North Korea had removed some of its loudspeakers along the border - days after South Korea dismantled some of its own.

Kim, the deputy director of North Korea's propaganda department, said Seoul's claim was an "unfounded unilateral supposition and a red herring".