An armoured personnel carrier stations by an intersection as Zimbabwean soldiers regulate traffic in Harare on November 15, 2017. [AFP PHOTO]

However, the soldiers denied that they had overthrown President Robert Mugabe, instead saying they were targeting "criminals" around the only ruler the country has known in its 37 years of independence.

Wednesday, soldiers seized the state broadcaster - Zimbabwe Broadcasting Corporation (ZBC). Armoured vehicles blocked roads to the main government offices, parliament and the courts in central Harare, while taxis ferried commuters to work nearby.

The atmosphere in the capital remained calm.

The military said Mugabe and his family were safe. According to a statement from the South African presidency, Mugabe spoke by telephone to President Jacob Zuma and told him he was confined to his home but was fine.

It was not clear whether the apparent military coup would bring a formal end to Mugabe's rule. The main goal of the generals appear to be preventing Mugabe's 52-year-old wife Grace from succeeding him.

But whether or not he remains in office, it is likely to mark the end of the total dominance of the country by Mugabe, the last of Africa's generation of state founders still in power.

Mugabe, still seen by many Africans as an anti-colonial hero, is reviled in the West as a despot whose disastrous handling of the economy and willingness to resort to violence to maintain power destroyed one of Africa's most promising states.

He plunged Zimbabwe into a fresh political crisis last week by firing his vice president and presumed successor. The generals believed that move was aimed at clearing a path for his wife, Grace, to take over and announced on Monday that they were prepared to "step in".

Targeting criminals

"We are only targeting criminals around him (Mugabe) who are committing crimes that are causing social and economic suffering in the country in order to bring them to justice," said Major General SB Moyo, Chief of Staff Logistics.

"As soon as we have accomplished our mission, we expect that the situation will return to normalcy," he said.

Whatever the final outcome, the events could signal a once-in-a-generation change for the southern African nation, once one of the continent's most prosperous, reduced to poverty by an economic crisis blamed on Mugabe.

Even many of Mugabe's most loyal supporters over the decades had come to oppose the rise of his wife, who courted the powerful youth wing of the ruling party but alienated the military, led by Mugabe's former guerrilla comrades from the 1970s independence struggle.

"This is a correction of a state that was careening off the cliff," said Chris Mutsvangwa, leader of the liberation war veterans.

"It's the end of a very painful and sad chapter in the history of a young nation, in which a dictator, as he became old, surrendered his court to a gang of thieves around his wife." he said.

The opposition Movement for Democratic Change called for a peaceful return to constitutional democracy, adding it hoped military intervention would lead to the "establishment of a stable, democratic and progressive nation state".

President Zuma - speaking on behalf of the Southern African Development Community (SADC) - expressed hope there would be no unconstitutional changes of government in Zimbabwe as that would be contrary to both SADC and African Union positions.

Zuma urged Zimbabwe's government and the military "to resolve the political impasse amicably".

Zimbabwe's economic decline over the past two decades has been a drag on the Southern African region. Millions of economic refugees have streamed out of the country, mostly to neighbouring South Africa.

Finance Minister Ignatius Chombo, a leading member of the ruling ZANU-PF party's 'G40' faction, led by Grace Mugabe, is said to have been detained by the military, a government source said.

Personnel carriers

Just 24 hours after Zimbabwe's military chief, General Constantino Chiwenga, threatened to intervene to end a purge of his allies in ZANU-PF, a Reuters reporter saw armoured personnel carriers on main roads around the capital.

Two hours later, the soldiers overran the headquarters of the ZBC, the state broadcaster and Mugabe's mouthpiece, and ordered staff to leave.

Shortly afterwards, three explosions rocked the centre of the capital.

The United States and Britain advised their citizens in Harare to stay indoors because of "political uncertainty".

The southern African nation had been on edge since Monday, when General Chiwenga said he was prepared to step in to end a purge of supporters of Emmerson Mnangagwa, the vice president sacked last week.

According to a trove of intelligence documents reviewed by Reuters this year, Mnangagwa had been planning to revitalise the economy by bringing back thousands of white farmers kicked off their land nearly two decades ago and patch up relations with the World Bank and IMF.

In the last year, a chronic shortage of dollars led to long queues outside banks and an economic and financial collapse that many feared would rival the meltdown of 2007-2008, when inflation hit 500 billion per cent.