North Korean leader Kim Jong Un blasts Donald Trump as "mentally deranged" and vows to make him pay.

North Korea said Friday it might test a hydrogen bomb on the Pacific Ocean after US President Donald Trump vowed to destroy the country, with leader Kim Jong Un promising to make a "mentally deranged" Trump pay dearly for his threats.

Kim, who has traded ever-more heightened rhetoric with Trump, did not specify what his response would be. His comments were believed to be the first direct message ever issued by a North Korean leader.

However, Kim's foreign minister, Ri Yong Ho, said North Korea could consider a hydrogen bomb test of an unprecedented scale on the Pacific Ocean, South Korea's Yonhap news agency reported.

KCNA North Korea's leader Kim Jong Un makes a statement regarding US President Donald Trump's speech at the UN general assembly.

Ri, who was talking to reporters in New York ahead of a planned address later this week, however also said he did not know Kim's exact thoughts, according to the report.

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Japan, the only country ever to suffer an atomic attack, described the threat as "totally unacceptable".

DONDI TAWATAO North Korean Foreign Minister Ri Yong Ho Ri Yong Ho said he believes the North could consider a hydrogen bomb test on the Pacific Ocean.

Trump said in his first address to the United Nations on Tuesday he would "totally destroy" North Korea, a country of 26 million people, if it threatened the United States and its allies, and called Kim a "rocket man" on a suicide mission.

Kim said the North would consider the "highest level of hard-line countermeasure in history" against the United States and that Trump's comments had confirmed his own nuclear programme was "the correct path".

Pyongyang conducted its sixth and largest nuclear test on September 3 and has launched dozens of missiles this year as it accelerates a programme aimed at enabling it to target the United States with a nuclear-tipped missile.

"I will surely and definitely tame the mentally deranged US dotard with fire," Kim said in the statement carried by the KCNA state news agency, referring to Trump.

SLEEPWALKING INTO WAR"

Vipin Narang, an associate professor of political science at Massachusetts Institute of Technology, said he could not recall such a statement in the first person, authored and signed by Kim.

"I don't think it's happened before. That's something to take seriously alone," he said.

The escalating rhetoric came even as U.N. Secretary-General Antonio Guterres called for statesmanship to avoid "sleepwalking" into a war.

South Korea, Russia and China all urged calm.

However, the rhetoric was starting to rattle some in the international community. French Sports Minister Laura Flessel said France's team would not travel to the 2018 Winter Olympic Games in South Korea if its security cannot be guaranteed.

The 2018 Games are to be staged in Pyeongchang, just 80km from the demilitarised zone between North and South Korea, the world's most heavily armed border.

Asian stocks fell and the Japanese yen and Swiss franc gained on the possibility of a hydrogen bomb test in the Pacific..