Russia's foreign minister has likened the war of words between Donald Trump and Kim Jong-un to a kindergarten fight between children.
The North Korean leader earlier labelled Mr Trump "mentally deranged" and a "dotard" after Mr Trump threatened to destroy his country.
Mr Trump responded with a tweet calling Kim Jong-un "a madman" who "will be tested like never before!".
He also mocked Kim Jong-un with a disparaging nickname, saying: "Rocket man is on a suicide mission.".
Image copyright Reuters/KCNA Image caption On Thursday North Korean state news agency released this picture of Mr Kim delivering his statement.
In an unprecedented personal statement, Mr Kim said Mr Trump would "pay dearly" for his speech, which he labelled "unprecedented rude nonsense".
Mr Trump on Thursday signed a new order boosting sanctions against North Korea, where the US treasury would target firms and financial institutions doing business with Pyongyang. »