Harare Zimbabwe's longtime ruler President Robert Mugabe is under house arrest in the capital Harare after the military seized power, sending the country into political turmoil.
Mugabe is "confined to his home" but "fine", South African President Jacob Zuma said on Wednesday after speaking on the telephone to the 93-year-old.
The secretary-general of the national war veterans association, Victor Matemadanda, said Mugabe should be removed as Zimbabwe's president and as the leader of the ruling Zanu-PF party.
Matemadanda is a key ally of the military as well as former vice president Emmerson Mnangagwa, who was fired by Mugabe last week.
Mugabe has ruled Zimbabwe with an iron fist for nearly four decades.
Zimbabwe's military effectively seized power in the early hours of Wednesday by taking control of Mugabe's offices, parliament, the airport and the state broadcaster.
"Robert Mugabe and his family's safety is guaranteed," a Zimbabwean military spokesman said, stating that the army was only "targeting criminals" in the administration.
Zuma urged Zimbabwe's military not to make "unconstitutional changes of government".
Speaking as chairman of the Southern African Development Community, Zuma demanded the military and government "resolve the political impasse amicably", while calling for "calm and restraint".
SADC was sending two special envoys to Zimbabwe, the South African defence minister and minister of state security, to meet with Mugabe and the military, Zuma added.
The atmosphere was tense in the capital, with tanks patrolling the city.
Mugabe's offices and parliament had been cordoned off by security forces. Hundreds of Zimbabweans were lining up at banks to withdraw money.
The move to seize power comes two days after top army general Constantino Chiwenga warned Mugabe the military would "step in" if he continued to expel people from the ruling party, including Mnangagwa.
Mugabe had also threatened to fire more than 100 officials linked to Mnangagwa.
The military has continued to deny it is carrying out a coup.
"We wish to make it abundantly clear that this is not a military takeover of government," said army spokesman Sibusiso Moyo, adding that the army was "only targeting criminals" who are "causing social and economic suffering".
"As soon as we have accomplished our mission we expect that the situation will return to normalcy," Moyo said.
The US embassy urged its citizens in Zimbabwe to "shelter in place" and said it had closed its embassy to the public because of the "ongoing public uncertainty". Britain also advised its citizens to stay at home.
The recent developments in Zimbabwe are "a matter of concern" for the European Union, said European Commission spokeswoman Catherine Ray.