Zimbabwean President Robert Mugabe has reportedly warned President Donald Trump that no country should monopolise ownership of nuclear weapons after the US leader threatened to "totally destroy" North Korea last week.

Mugabe said this on Monday following his arrival in Harare from New York where he attended the 72nd ordinary session of the United Nations General Assembly (UNGA).

Trump stunned UN watchers on Tuesday last week by threatening to "totally destroy" North Korea, describing its leader Kim Jong-Un as "Rocket Man".

But, according to the state-owned Herald newspaper, while addressing his Zanu-PF party supporters who gathered to welcome him back, Mugabe said he maintained that all nations were equal before international law and that "no country should be allowed to bully others on the basis of its military might".

Said Mugabe: "Each and every country has the power to rule itself, no matter how small… No country is too small. So we are just warning him ([rump]," Mugabe said while speaking in Shona.

'Are we having a return of Goliath'

Mugabe did not mince words while addressing the UNGA last week, mocking the US president as the "Giant Gold Goliath".

The 93-year-old veteran leader took Trump to task both on policy and appearance.

"Some of us were," Mugabe said, pausing for emphasis, "embarrassed, if not frightened, by what appeared to be the return of the biblical Giant Gold Goliath".

"Are we having a return of Goliath to our midst, who threatens the extinction of other countries?" he asked, triggering applause in the hall as two junior US diplomats listened expressionless.

"And may I say to the United States president, Mr Trump, please blow your trumpet - blow your trumpet in a musical way towards the values of unity, peace, co-operation, togetherness, dialogue, which we have always stood for and which are well-writ in our very sacred document, the Charter of the United Nations."