North Korea is working to ensure its nuclear and ballistic missile capabilities cannot be destroyed by military strikes, UN monitors say ahead of a meeting between US and North Korean officials to prepare a second denuclearisation summit.

United Nations Secretary-General Antonio Guterres tells the UN Security Council that he is alarmed by the risk of military escalation on the Korean Peninsula.

Malaysia expels the North Korean ambassador to the country, declaring him "persona non grata" and asking the envoy to leave Malaysia within 48 hours.

North Korea warns the US will "pay dearly" if it puts Pyongyang on a terror list over the killing of its leader's half-brother, as a suspect in the murder claims he was the victim of a conspiracy.

US President Barack Obama dismisses North Korea's proposal to suspend nuclear tests if the US ends its annual military exercises with the South.