North Korean leader Kim Jong Un warned Friday that he could take the "highest-level" of retaliatory action against U.S. President Donald Trump following his "unprecedented rude nonsense" speech this week to the United Nations.

"Now that Trump has...insulted me and my country in front of the eyes of the world and made the most ferocious declaration of a war...we will consider with seriousness exercising of a corresponding, highest level of hard-line countermeasure in history," Kim said in a statement, carried by the country's official Korean Central News Agency.

(KNS)

The KCNA report of Kim's first-ever statement of its kind came just hours after Trump ordered fresh unilateral sanctions taking aim at North Korea's nuclear and ballistic missile programs by sanctioning banks, other entities or individuals that finance and facilitate trade with the country.

"It could be the most powerful detonation of an H-bomb in the Pacific Ocean," North Korean Foreign Minister Ri Yong Ho, who is in New York to attend the U.N. General Assembly, later told reporters.

Ri also said, "We have no idea about what actions could be taken as it will be ordered" by Kim, when asked what the North Korean leader meant by the "highest-level" of action.

Kim pledged to have Trump "pay dearly" for his speech, without specifying what the countermeasure may be.

"This is not a rhetorical expression loved by Trump," Kim was quoted as saying. "Whatever Trump might have expected, he will face results beyond his expectation."

In his debut address to world leaders at the annual U.N. meeting on Tuesday, Trump said the United States will have "no choice but to totally destroy North Korea" if it is forced to defend itself or its allies.

Trump even went on to call the North Korean leader "Rocket Man," on "a suicide mission for himself and for his regime."

In return, Kim concluded the statement by saying he will "surely and definitely tame the mentally deranged U.S. dotard with fire."

Deciding to continue the war of words with Kim, Trump then countered with a Twitter outburst on Friday night in which he said the North Korean leader, "who is obviously a madman who doesn't mind starving or killing his people, will be tested like never before!"

Kim said Trump's remarks at the United Nations were "unprecedented rude nonsense one has never heard from any of his predecessors."

While lecturing Trump to be more prudent in selecting words when making a speech, Kim said he cannot avoid thinking that the U.S. president is "unfit to hold the prerogative of supreme command of a country."

"He is surely a rogue and a gangster fond of playing with fire, rather than a politician," Kim said.

Some minutes before North Korea's state broadcaster was to report about Kim's statement for the first time in its 3 p.m. news program, a number of young and old gathered in front of a big public TV screen outside the Pyongyang railway station.

"I can't really bear with this. What's going on with that guy (Trump) who always makes accusations to our country? We have nothing to afraid of," Ri Chung Song said after watching the program. "If they fire, we will fire. Let's make that clear."

"I fully support the statement," the 40-year-old man said.

(Getty)

The rhetorical battle between the two countries already existed before Trump's speech to the United Nations, amid high tensions over North Korea's continued nuclear and missile tests.

North Korea conducted a test of what it claimed was a hydrogen bomb that can be placed on an intercontinental ballistic missile on Sept. 3.

In addition to its sixth and most powerful nuclear test, it fired the second intermediate-range ballistic missile over Japan in less than a month one week ago.

Prior to those weapons tests, North Korea fired in July two ICBMs potentially capable of reaching the mainland United States and threatened to send ballistic missiles near the U.S. Pacific territory of Guam.

Kim has never released a statement in his own name before, nor did late leaders Kim Il Sung and Kim Jong Il, according to South Korea's Unification Ministry, which handles North Korea ties.

This suggests that North Korea is unlikely to back down from its weapons program and standoff with the United States anytime soon, despite repeated international condemnations and sanctions.

Following Trump's remarks at the United Nations, Kim said he is more convinced, rather than frightened, that "the path I chose is correct and that it is the one I have to follow to the last."

Kim issued the statement in the name of chairman of the State Affairs Commission at the building of the Central Committee of the Workers' Party in Pyongyang on Thursday, according to KCNA.

The additional unilateral sanctions, announced by Trump as he met with the leaders of Japan and South Korea in New York, enable Washington to target anyone trading in goods, services or technology with North Korea and ban them from making transactions through the U.S. financial system.

"Many countries are working with us to increase economic and diplomatic pressure on North Korea, but I continue to call on all those responsible nations to enforce and implement U.N. sanctions and impose their own measures like the ones I am announcing today," Trump said.