Zimbabwe's military has placed President Robert Mugabe under house arrest in the capital Harare, South African President Jacob Zuma says.
Soldiers seal off a main road to the parliament building in Harare. Photo: AFP
Mr Mugabe told Mr Zuma in a phone call that he was fine, the South African leader's office said.
Troops are patrolling the capital, Harare, after they seized state TV and said they were targeting "criminals".
The move may be a bid to replace Mr Mugabe with his sacked deputy, Emmerson Mnangagwa, the BBC reports.
Mr Mnangagwa's dismissal last week left Mr Mugabe's wife Grace as the president's likely successor.
Mr Mugabe, 93, has dominated the country's political scene since it gained independence from the UK in 1980.
After days of tension and rumour, soldiers seized the state broadcaster ZBC late on Tuesday.
A Zimbabwean army officer, Major General Sibusiso Moyo, went on air and denied there was a coup, but said the military was targeting "criminals" around President Mugabe.
Maj Gen Moyo also said Mr Mugabe and his family were "safe and sound and their security is guaranteed". It is not clear who is leading the military action.
Since then military vehicles have been out on the streets of Harare, while gunfire has been heard from northern suburbs where Mr Mugabe and a number of government officials live.
In a statement, Mr Zuma's office said: "President Zuma spoke to President Robert Mugabe earlier today who indicated that he was confined to his home but said that he was fine."
Robert Mugabe, 93, has dominated the country's political scene since it gained independence in 1980. Photo: AFP
Old guard reasserts authority
The unrest in Zimbabwe is all about the leadership succession, as Mr Mugabe's powers finally falter.
The people who fought in the 1970s guerrilla war against white minority rule still dominate Zimbabwe's government, and especially its security forces, and they are worried about losing that power, and the wealth it generates.
In his statement on Monday, army chief General Constantino Chiwenga warned against the "purging, which is clearly targeting members of the party with a liberation background".
This was obviously a reference to the sacking last week of Mr Mugabe's once loyal deputy, Mr Mnangagwa, a former defence minister, spy chief and veteran of the war of independence.
General Constantino Chiwenga, head of the army, Photo: AFP
He and Grace Mugabe, who is four decades younger than her husband, had been seen as the main candidates to succeed Mr Mugabe.
Mrs Mugabe's supporters are known as "Generation 40" or "G40" - a name which signals a changing of the guard in Zimbabwe, at least partially, 37 years after independence.
This military action is the old guard reasserting its authority.
Mr Mugabe was the political leader of the guerrilla war and the army has always professed loyalty to him, until he explicitly came out in favour of his wife taking over from him.
An armoured personnel carrier in Harare on Tuesday. Photo: AFP
