North Korea has labelled Joe Biden a "fool of low IQ" and an "imbecile bereft of elementary quality as a human being" after the US presidential hopeful called leader Kim Jong-un a tyrant during a speech.
Pyongyang's official Korean Central News Agency said the former US vice president had insulted the country's supreme leadership and committed an "intolerable and serious politically-motivated provocation".
Biden during a campaign event in Philadelphia accused President Donald Trump of cosying up to "dictators and tyrants" like Kim and Russia's Vladimir Putin.
"What he uttered is just sophism of an imbecile bereft of elementary quality as a human being, let alone a politician," KCNA said.
After two summits with Kim Jong-un, Donald Trump says North Korea is not ready to negotiate. Source: AAP
"There is non-stop comment over his bid for a candidacy that he is not worth pinning hope on, backed by the jeer that he is a fool of low IQ.
"Yet, he is self-praising himself as being the most popular presidential candidate. This is enough to make a cat laugh."
North Korea has often unleashed crude insults against the US and South Korean politicians in past years to criticise what it saw as insults to its leadership or hostile diplomatic and military policies.
The insults have included racist and sexist diatribes, including when the North called former President Barack Obama "a monkey" and former South Korean President Park Geun-Hye, the country's first female leader, a prostitute.
During tensions created by a provocative run in missile tests in 2017, Kim called Trump a "mentally deranged US dotard" after he said the US would "totally destroy North Korea" if forced to defend itself or its allies.
