North Korea's most senior defector has claimed Kim Jong Un would fire a suicidal nuclear salvo at Los Angeles if his rule was threatened.

The dictator would "press the button" to destroy the Californian city despite the inevitable consequences, Thae Yong-ho, the former deputy ambassador in London, said.

He told the BBC's Victoria Derbyshire Show he thought the dictator "will press the button on these dangerous weapons when he thinks that his rule and his dynasty is threatened".

Asked if Mr Kim would act even knowing a nuclear attack on the US mainland would mean his destruction, Mr Thae replied: "Yes."

Mr Thae has previously said the Kim regime is aiming to complete its development of nuclear weapons by the end of 2017, and would not stop even if it was offered trillions of dollars to do so.

Pyongyang has asserted it will conduct its next nuclear missile test "anytime and anywhere".

Meanwhile, President Donald Trump has announced the development of a "state-of-the-art" missile defence system to protect the US from Iran and North Korea, according to a statement posted to the White House website minutes after the new commander-in-chief was sworn into office.

Mr Thae added: "Kim Jong Un knows quite well that a nuclear weapon is the only guarantee for his rule. If he lose the power then it is his last day. He may do anything."