Robert Mugabe's exit as Zimbabwe's president is being hailed a 'miracle' by a longstanding campaigner in the country.

Ben Freeth, who rose to prominence after taking Mugabe to court – a battle that featured in the documentary Mugabe and the White African – was speaking to Christian Today from Harare as the 93-year-old president's successor was sworn in on Friday.

'It's incredible. It is unbelievable what has taken place,' he said.

The army swept to power early last Wednesday and took control of the state broadcaster as well as key institutions. Mugabe, known as the 'grand old man' of African politics, clung to the presidency and initially refused to quit before eventually resigning earlier this week.

The peaceful transition is a surprise to many who expected Mugabe's departure after 37-years in power to be bloody. Freeth hailed it a 'miracle'.

He told Christian Today: 'There has not been a drop of blood split in this whole coup. There has been process. There has been constitutionality.'

He said: 'God's hand has been so unbelievably present in this whole thing that has taken place right the way through.'

Mugabe's resignation prompted scenes of wild excitement as Zimbabwe saw the back of the only president it has known since British colonial rule left in 1980.

'There has just been joy. Absolute joy. People have been completely bowled over about the fact that after 37 years Mugabe has walked out voluntarily,' said Freeth.

'People have just been jubilant but already there is a slight fear of the future,' he added, referring to the former vice-president, Emmerson Mnangagwa, who is due to be sworn in as the new leader on Friday.

'He has a background of being part of the oppression, part of the system, part of the genocide. But we remain hopeful. He has said there will be a free and fair elections next year.'

Mnangagwa, nicknamned the 'Crocodile' returned to Zimbabwe on Wednesday after he fled for his life when Mugabe fired him last week.

'We hope and pray,' said Freeth. 'People are uncertain at this stage.'

But he went on: 'This is God. The world must know that this is God. God is able to work his miraculous way in nations. This really is an instance of God's hand.'

Military rulers have agreed to give Mugabe immunity from prosecution and insisted he can live safely in Zimbabwe.

A government source confirmed to Reuters that Mugabe had told negotiators he wanted to die in Zimbabwe and had no plans to live in exile.

'For him it was very important that he be guaranteed security to stay in the country ... although that will not stop him from travelling abroad when he wants to or has to,' the source said.

A second source added: 'The outgoing president is obviously aware of the public hostility to his wife [Grace], the anger in some circles about the manner in which she conducted herself and approached Zanu-PF party politics.

'In that regard, it became necessary to also assure him that his whole family, including the wife, would be safe and secure.

'It was very emotional for him and he was forceful about it.'