North Korean leader Kim Jong Un called Mr Donald Trump a "dotard" and threatened to take the most "hardline countermeasure in history" after the US President warned that America, if threatened, would "totally destroy" the "rocket man" and his communist state.
As the verbal barbs took on an increasingly personal and bellicose tone, jittery Asian stock markets swiftly beat a retreat.
Mr Kim, in a rare media statement in which he described Mr Trump variously as "mentally deranged", "a dotard" and "a gangster fond of playing with fire", warned Mr Trump that he will pay dearly for the threat he made in a speech at the United Nations on Tuesday.
Dotard and the other words appeared in a translation by the state news agency KCNA yesterday. Dotard, which means old fool, became a top trending word on Google and Twitter.
As to what the most hardline action could refer to, North Korean Foreign Minister Ri Yong Ho told reporters in New York, where he is attending the UN General Assembly, that it could be "the most powerful detonation of an H-bomb (hydrogen bomb) in the Pacific".
The escalating rhetoric came shortly after Mr Trump ordered even more sanctions against the North as punishment for conducting its sixth nuclear test on Sept 3.
In Beijing, a Foreign Ministry spokesman urged relevant parties to exercise restraint and stop provoking each other. Foreign Minister Wang Yi separately said Pyong- yang should stop persisting on a dangerous course.
South Korean President Moon Jae In told the North to end the provocations, adding that continued sabre-rattling would leave the world with no option but to pressure North Korea "with one voice".
Japan's Chief Cabinet Secretary Yoshihide Suga lambasted North Korea's remarks and behaviour as "absolutely unacceptable".
Japanese warships conducted drills with Japan-based US Navy carrier Ronald Reagan in waters south of the Korean peninsula in a show of strength against Pyongyang's nuclear threat. The drills have been ongoing since Sept 11.
Analysts said they are not surprised by the North's stinging rhetoric, noting that Mr Trump too used provocative words in his UN speech. Calling Mr Kim a "rocket man on a suicide mission", he said the US, if forced to defend itself or its allies, will have to "totally destroy" North Korea.
In a tweet after Mr Kim's statement yesterday, Mr Trump, who at 71 is more than twice Mr Kim's age, called him "a madman" who "will be tested like never before".
Dr Bong Young Shik of Yonsei University's Institute for North Korean Studies told The Straits Times that Mr Kim "felt insulted and he is angry", which fuelled the need to further ratchet up tensions.
He said Pyongyang could indeed send a ship out to the Pacific Ocean with materials to conduct a nuclear test, fire a nuclear-tipped missile over Japan into the ocean or simply not follow through with its threat.
But one thing is for sure, he said. "North Korea will continue to test nuclear warheads and ICBMs (intercontinental ballistic missiles) because they are far from acquiring... nuclear strike capability."
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