Kim Jong-Un has threatened to reduce the US ‘to ashes’ with nuclear weapons if American fires ‘even a single bullet’ at North Korea.

Pyongyang said it would use its ‘invincible Hwasong rockets tipped with nuclear warheads’ to defend its territory as tensions with South Korea continued to escalate.

It comes as Seoul insisted North Korea’s latest rocket-engine test showed ‘meaningful’ progress and as an an analyst said the secretive state had taken a dangerous step towards its goal of developing a rocket that could hit the United States.