South Korean President Lee Jae Myung vowed on Friday to "respect" North Korea's political system and build "military trust", a day after Pyongyang said it had no interest in improving relations with Seoul.

The North Korean leader's powerful sister said on Thursday that the country has never taken down propaganda loudspeakers and will not do so, calling South Korea's belief that Pyongyang was responding to its peace overtures a "pipedream.

South Korea’s birth rate has dropped throughout much of the past decade, spelling trouble for the military as regional threats and global conflicts simmer.