Mugabe is reportedly resisting a potential exit for him through mediation between Fidelis Mukonori, a Catholic priest, and the military.
The 93-year-old President reportedly said he can only be removed through a party leadership vote.
Morgan Tsvangirai, opposition leader, who has been receiving cancer treatment outside Zimbabwe, returned to Harare, the state capital, late Wednesday, a party spokesman said, fuelling speculation about a post-Mugabe political settlement.
Local media reported that South Africa’s defence and state security ministers, dispatched by President Jacob Zuma as regional envoys, arrived Harare Wednesday night and were expected to meet both Mugabe and the military.
Their goal, however, remains unknown.
Zuma had earlier called for “calm and restraint” and asked the defense forces “to ensure that peace and stability are not undermined in Zimbabwe”.
The South African presidency said Mugabe had told Zuma over the phone that he was confined to his home but was otherwise fine and the military said it was keeping him and his family safe.
Mugabe had last week by fired Emmerson Mnangagwa, his vice president and presumed successor, known as the “crocodile” – for showing “traits of disloyalty”.
The military believed the move was aimed at clearing a path for Grace, Mugabe’s wife, to take over and said on Monday they were prepared to “step in” if purges of their allies did not end.