"It's done. President Mnangagwa will be sworn in on Friday," Zimbabwe's ruling ZANU-PF party said on Twitter. "The new era has arrived, our new President," the party added, attaching a photo of Mnangagwa, 75.

Earlier, state-owned Zimbabwe Broadcasting Corp (ZBC) said the ruling party had selected Mnangagwa to replace Mugabe, the nonagenarian who had been in power since 1980 but was finally forced to quit after military intervention and mass protests.

Advocate Jacob Francis Mudenda, a ZANU-PF member, said Parliament informed the Chief Secretary to the Office of President of Mnangagwa's nomination, the Guardian reported.

Mnangagwa fled for safety to South Africa two weeks ago when he was sacked by Mugabe, triggering a political crisis that culminated in the resignation of the 93-year-old autocrat on Tuesday.

Mnangagwa touched down at a military air base in Harare on Wednesday on a flight from South Africa. Car horns and celebrations greeted the motorcade believed to be carrying Mnangagwa as it passed through the Zimbabwean capital on the way to the ruling party headquarters.

Mugabe, who ruled the country with an iron grip for 37 long years, finally caved to popular and political pressure hours after Parliament launched proceedings to impeach him. 

He had refused to leave office during eight days of drama and uncertainty that began with a military takeover last week.

Harare was quiet on Wednesday morning after a night of joyous celebration. Traffic was normal and many people were going to work. 

"It's a new day for Zimbabwe. We are smiling," said Lovemore Simbeli, 19, as he sold newspapers with frontpages splashed with headlines announcing Mugabe's departure.

Attention now turns to Mnangagwa, once one of Mugabe's closest aides and one of the most powerful officials within the ruling Zanu-PF party. 

Mugabe sacked Mnangagwa in a bid to clear the way to power for his ambitious but unpopular 52-year-old wife Grace Mugabe and her G40 faction.

It is unclear whether Mugabe and his wife will remain in Zimbabwe, where both would be seen as a potential threat to Mnangagwa or any other new leader and could face prosecution.

Mnangagwa on Tuesday night congratulated the people of Zimbabwe "on reaching this historic moment". 

"Together we will ensure a peaceful transition to the consolidation of our democracy and bring in a fresh start for all Zimbabweans and foster peace and unity."