Zimbabwe’s military has seized state TV, saying it is targeting people close to President Robert Mugabe for causing “social and economic suffering”.
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.
Heavy gun and artillery fire could be heard in northern parts of the capital Harare early on Wednesday.
The army action comes after Mr Mugabe sacked Vice-President Emmerson Mnangagwa, amid a row over succession.
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There was no immediate word from Mugabe but Zimbabwe’s envoy to South Africa, Isaac Moyo, said the government was “intact”.
Mugabe, 93, has dominated the impoverished country’s political scene since independence from the UK in 1980.
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.