US Republican Senator Lindsey Graham told BBC HARDtalk on Saturday that an American first military strike against North Korea is "inevitable" if something does not change.

Mr Graham was speaking to programme host Stephen Sackur at the Ambrosetti Forum in Italy, just hours before North Korea's new claim of a successful hydrogen bomb test.

"I am 100% certain that if Kim Jong-un continues to develop missile technology that can hit America, if diplomacy fails to stop him, there will be an attack by the US against his weapon system. I'm assuming the worst, I'm assuming we drop one bomb, he fires at South Korea and maybe Japan. Let me tell you how the war ends: it ends with his utter destruction. Thousands of people could be killed or maimed.

"There's a lot at stake here. Let me ask you: why would the world allow him [Kim Jong-un] to get a hydrogen bomb with a missile to deliver it anywhere in the world? Why would we do that?"