Declared a national hero within hours of his death by the long-serving aide who succeeded him as president, Mugabe was one of the most polarising figures in his continent's history - a giant of African liberation whose regime finally ended in ignominy when he was overthrown by his own army.

He died on Friday in Singapore, where he had long received medical treatment.

Granting him the status of national hero in a televised address, President Emmerson Mnangagwa praised Mugabe an icon and a "remarkable statesman of our century".

"On the backdrop and solid foundation of the first republic which he moulded as its leader, we today recover and grow," Mnangagwa said.

Mnangagwa, Mugabe's one-time security chief who helped oust him from power, had returned home earlier in the day after cutting short a trip to a World Economic Forum summit in South Africa.

Tributes poured in from African leaders. South Africa's government mourned a "fearless pan-Africanist liberation fighter".

Kenya's President Uhuru Kenyatta hailed a "man of courage who was never afraid to fight for what he believed in, even when it was not popular".

At home, even foes paid respects.

"He was a colossus on the Zimbabwean stage and his enduring positive legacy will be his role in ending white minority rule & expanding a quality education to all Zimbabweans," tweeted David Coltart, an opposition senator and rights lawyer.

Others, including the prime minister of former colonial power Britain, said Mugabe's legacy was overshadowed by the harm he did to his people

"We of course express our condolences to those who mourn, but know that for many he was a barrier to a better future," a spokeswoman for Boris Johnson said.

"Under his rule the people of Zimbabwe suffered greatly as he impoverished their country and sanctioned the use of violence against them."

On the streets, the response was mostly more generous.

"He was iconic, he was an African legend. His only mistake was that he overstayed in power," Harare resident Onwell Samukanya said.

Mugabe was feted as a champion of racial reconciliation when he first came to power in 1980 in one of the last African states to throw off white colonial rule.

By the time he was toppled to wild celebrations across the country of 13 million, he was viewed by many at home and abroad as a power-obsessed autocrat who unleashed death squads, rigged elections and ruined the economy to keep control.

Mugabe called his departure an "unconstitutional and humiliating" betrayal. Confined to his sprawling Harare mansion, he stayed bitter to the end.

Just under two years after his departure, Zimbabwe has yet to recover its lustre.

Beset by triple-digit inflation, rolling power cuts and shortages of basic goods, the economy is mired in its worst crisis in a decade, while political opponents say a clampdown on dissent by Mnangagwa's government has revived memories of the Mugabe era.

Australian Associated Press