(CNN) US President Donald Trump may claim he would never insult Kim Jong Un , but North Korea clearly thinks differently.

A furious commentary published in a state-run newspaper Wednesday said Trump had displayed his "true colors as an old lunatic, mean trickster and human reject" during his recent visit to the Korean Peninsula.

"The worst crime for which he can never be pardoned is that he dared malignantly hurt the dignity of the supreme leadership of (North Korea)," the Rodong Sinmun commentary said.

"Trump, who is no more than an old slave of money, dared point an accusing finger at the sun. He should know that he is just a hideous criminal sentenced to death by the Korean people. He will be forced to pay dearly for his blasphemy any moment."

Rodong Sinmun is the official newspaper of North Korea's ruling Workers' Party, and the commentary was also published by state news agency KCNA.

North Korea has previously boasted of its ability to strike the US with intercontinental ballistic missiles (ICBM) if Washington continues what Pyongyang views as acts of aggression against North Korea.

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Speech angered Pyongyang

John Delury, an expert on North Korea at Seoul's Yonsei University, said Trump's speech was particularly inflammatory from Pyongyang's perspective, "and it was inevitable there would be a very strong reaction."

While Trump's rhetoric in Seoul was praised by some observers for avoiding the type of "fire and fury" language he has used in the past, North Korea watchers have warned that direct criticism of the Kim dynasty -- which has ruled North Korea since its founding -- and the country's political system, is far more likely to rile Pyongyang.

"I have (come) to this peninsula to deliver a message directly to the leader of the North Korean dictatorship," Trump said last week. "Every step you take down this dark path increases the peril you face."

"North Korea is not the paradise your grandfather envisioned," he added. "It is a hell that no person deserves."

Delury said the issue is, "when President Trump gives speeches like this, how much does the North Korean system sort of contract around offending the dignity of the leader."

"That's the danger in a speech like that, if the Trump administration wants any kind of diplomacy at all, how much they kill that possibility (by insulting Kim)," he added.

CNN correspondent Will Ripley, who was in Pyongyang at the time of Trump's speech, said last week this type of language is likely to be "more infuriating to the North Koreans than the fiery rhetoric (Trump has) used before," as the US leader "directly criticized their ideology and authoritarian system."

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Trump and Kim

During his Asia trip, while Trump maintained absolute US opposition to North Korea's nuclear program and the threat of heavy retaliation for any actions against the US or its allies, he did appear to raise the possibility of future talks with Pyongyang.

Asked about the possibility of becoming friends with the North Korean leader during a news conference in Vietnam, Trump did not rule it out.

"Strange things happen in life. That might be a strange thing that happens. But it is certainly a possibility," Trump said. "If that did happen, it would be a good thing for, I can tell you, for North Korea. But it would also be good for lots of other places, and it would be good for the world."

However, he also sarcastically responded to insults in North Korean state media in a tweet mentioning the country's leader

"Why would Kim Jong Un insult me by calling me 'old,' when I would never call him 'short and fat?' Oh well, I try so hard to be his friend -- and maybe someday that will happen!" Trump tweeted.

Delury said the Rodong Sinmun commentary was a "tit for tat" response to Trump's recent rhetoric, but added it remains to be seen if this blowing off of steam will be enough for North Korea's system to absorb the insults to its leader, or if more action will be needed.