President Robert Mugabe and his family have been detained following military intervention in capital Harare, which an army spokesman and the ruling party insisted Wednesday was "not a coup".
Troops in Zimbabwe's capital Harare have reportedly seized the country's state broadcaster ZBC and loud explosions have been heard in the city, prompting further speculation of a coup.
He added that things will return to normal as soon as the mission is accomplished.
ZANU-PF responded by accusing the commander of "treasonable conduct meant to disturb national peace and incite insurrection". Soldiers indeed have the president and his presidential guard under siege.
Areport said they would face charges of undermining the authority of the President, by singing "We hate what you're doing" as the first lady spoke.
Chiwenga's unprecedented statement represented a major escalation of the struggle to succeed Mugabe, the only leader Zimbabwe has known since it gained independence from Britain in 1980.
Mugabe fired Vice President Emerson Mnangagwa last week.
Image Robert Mugabe shakes hands with then prime minister Margaret Thatcher in 1980
He says it is important to remember that Mr Mugabe is not being challenged by the Western governments he has warned against for decades, or by Zimbabwe's political opposition, or by a mass uprising against economic hardship.
Grace Mugabe has drawn the ire of Zimbabweans for appearing to be out of touch.
A week of turmoil has followed the sacking of Zimbabwe's deputy leader Emmerson Mnangagwa by President Mugabe.
The US embassy in Harare tweeted that it would be closed on Wednesday "due to ongoing uncertainty".
Mugabe's firing of Vice President Emmerson Mnangagwa, his right-hand man for almost four decades, stunned the nation.
In a statement attributed to Mnangagwa at the time he reportedly left for self-imposed exile, he promised to return to Zimbabwe to "lead" the country, warning Mugabe that the ZANU PF party was not his personal property.
Grace Mugabe's rise has brought her into conflict with the independence-era war veterans, who once enjoyed a privileged role in the ruling party under Mugabe, but who have in recent years been banished from senior government and party roles.
"Usually, the police support unit quickly rushes onto the streets and it was feared they would mobilise the youths and give them guns so they could fight back, but the military boxed them deep in the night and took over all strategic points there", a witness said.
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