The military has seized control in Zimbabwe and has said President Robert Mugabe, in power since 1980, is safe.
After seizing state TV, an army spokesman announced it was targeting people close to Mr Mugabe who had caused "social and economic suffering".
Messages attributed to a ruling party Twitter account described the takeover as a "bloodless transition".
The move came after Mr Mugabe sacked his deputy, Emmerson Mnangagwa, in favour of his wife.
A statement read out by a general on air denied it was a coup and said Mr Mugabe was safe, but did not say where.
There was no immediate word from Mr Mugabe himself.
Mr Mugabe, 93, has dominated the impoverished country's political scene since independence from the UK.
The UK Foreign Office advised Britons "currently in Harare to remain safely at home or in their accommodation until the situation becomes clearer", while the US embassy in Harare advised US citizens in Zimbabwe to "shelter in place" until further notice.
Due to ongoing uncertainty in Zimbabwe, the U.S. Embassy in Harare will be minimally staffed and closed to the public on November 15. Embassy personnel will continue to monitor the situation closely.
Soldiers overran the headquarters of the ZBC broadcaster after armoured vehicles took up position on roads around Harare on Tuesday.
Maj Gen Sibusiso Moyo went on air to say the military wished to "assure the nation that his Excellency the president... and his family are safe and sound and their security is guaranteed".
Soldiers stand beside military vehicles just outside Harare, Zimbabwe, 14
Armoured vehicles were seen taking up positions on roads outside Harare on Tuesday.
"We are only targeting criminals around him who are committing crimes... that are causing social and economic suffering in the country," he said.
"As soon as we have accomplished our mission, we expect that the situation will return to normalcy."