North Korea agrees to allow international inspectors to observe a "permanent dismantlement" of its key missile facilities, and will take additional steps such as closing its main Yongbyon nuclear complex if the United States takes reciprocal measures, South Korea's President Moon Jae-in says.

North Korean leader Kim Jong Un yesterday said his "historic" summit with US President Donald Trump in Singapore stabilised regional security, and that he expected further progress at an inter-Korean summit aimed at reviving stalled nuclear diplomacy.

North Korea is willing to hold talks with the United States on denuclearisation and will suspend nuclear tests while those talks are under way, the South says after a delegation returned from the North where it met leader Kim Jong Un.

North Korea says it will reopen a long-closed border hotline with South Korea, hours after US President Donald Trump appeared to mock the North's leader by saying he has a "bigger and more powerful" nuclear button than Kim Jong Un.