The AU had "serious concern" at the situation and "reiterates its full support to the country's legal institutions", the statement said.
Tendai Biti spoke to South African broadcaster eNCA as the 93-year-old Mugabe was said to be in army custody after an unprecedented public rift with the military.
The South African President will send an advanced team of military leaders to engage all key stakeholders in Zimbabwe's polity.
The on-going political crisis will be of enormous concern to the various worldwide organizations Zimbabwe belongs to namely; the United Nations, African Union and South Africa Development Commission (SADC), amongst others.
Zuma also said "he had spoken to Mr Mugabe, who had indicated that he "was confined to his home, but said that he was fine", according to another report seen by APA.
Governments in Malawi and the rest of Southern Africa are closely monitoring developments in Zimbabwe where the military has intervened in a power struggle that has rocked the ruling Zimbabwe African National Union known in short as Zanu-PF.
The South African president said southern Africa's regional body will "closely monitor the situation and remains ready to assist where necessary". A top police official who insisted on anonymity because he was not authorized to speak to the press told The Associated Press that all police on leave have been ordered to return to their posts immediately.
Soldiers had earlier on Wednesday morning announced on state radio what appeared to be a coup against President Robert Mugabe who has been ruling the country since its independence in 1980. There were armoured vehicles and soldiers on the streets of central Harare.
The Chairperson of the AU Commission, Moussa Faki Mahamat, on Wednesday urged Zimbabweans to address the current situation in the country in accordance with the country's Constitution.
Citizens await an announcement from the meeting on the way forward even though the country has largely been peaceful since the army took over on Wednesday. On Tuesday afternoon, the military rolled out tanks from the barracks and stationed them on the road from the army base to Harare city centre.