US President Donald Trump is "mentally deranged" and will "pay dearly" for his threat to destroy North Korea, Kim Jong-Un said Friday, as his foreign minister hinted the regime may explode a hydrogen bomb over the Pacific Ocean.
In a rare personal attack published hours after Washington announced tougher sanctions, the North Korean leader took aim at Trump over his maiden speech to the UN General Assembly in which he branded Kim "Rocket Man" and threatened to "totally destroy North Korea".
Trump "insulted me and my country in front of the eyes of the world and made the most ferocious declaration of a war in history", Kim said, according to the official Korean Central News Agency.
"I will make the man holding the prerogative of the supreme command in the US pay dearly for his speech," which he called "unprecedented rude nonsense".
The dispatch was accompanied by a photo of the North Korean leader sitting behind a desk holding a piece of paper.
"I will surely and definitely tame the mentally deranged US dotard with fire," he said.
On the fringes of the UN General Assembly in New York, North Korean Foreign Minister Ri Yong-ho told reporters Pyongyang might now consider detonating a hydrogen bomb outside its territory.
"I think that it could be an H-bomb test at an unprecedented level perhaps over the Pacific," he said.
However, he added: "It is up to our leader so I do not know well."
Kim’s retort was published after Trump announced he had signed an executive order to ban firms from operating in the United States if they deal with North Korea.
US President Donald Trump threatened in his speech at the UN to ’totally destroy’ North Korea if it attacks the US or its allies. Photo: Reuters
The move was the latest effort to tighten the screws on Pyongyang over its banned weapons programmes, which have quickened with its sixth nuclear test -- the largest yet -- and the firing of two missiles over Japan.
It also came after the UN Security Council agreed a further set of sanctions on North Korea, aimed at reducing its ability to trade with the outside world.
Analysts say the sanctions show no signs of working, and cautioned that the increasingly ill-tempered and personal exchanges between Washington and Pyongyang did not auger well.
"There are some very dangerous things that could come that move this from theatre to reality. This is the time to be heading them off, not making them feel inevitable," said John Delury of Yonsei University in Seoul.
He added that Kim’s rare first-person statement, which was expected to be broadcast on local television, could also have been aimed at North Koreans.
"He is telling his country that the American president at the United Nations said he is going to totally destroy us -- he is going to totally destroy you -- but I am not going to let that happen," Delury told AFP.