A war of words between North Korea and US President Donald Trump over the death of an American student has escalated, with Pyongyang describing the American leader as an "old lunatic".
As our Washington correspondent John Clarke reports, the death of Otto Warmbier remains a mystery despite a coroner's inquest, and the causes for his fatal injury might never be known.
IN: "Otto Warmbier was...
OUT: SOC
DUR: 49"