Harare – Thousands of Zimbabweans are expected to demand President Robert Mugabe's resignation on Saturday at a march in the capital, Harare.
The march to State House is backed by the army, which seized power on Wednesday.
Demonstration is also expected to take place at City Hall in Bulawayo, the second city.
Zimbabwe has been in political turmoil since the early hours of Wednesday, when the country's armed forces seized power and placed Mugabe - who leads the Zanu-PF party, under house arrest.
March organiser Chris Mutsvangwa, who leads the Zimbabwe National Liberation War Veterans Association, said the rare show of public defiance against the president is not a Zanu-PF affair, but "a show of people's force" against Mugabe's 37-year rule.
William Gerald Lumumba Mutumanje - popularly known as Acie Lumumba, an activist who was expelled as the Zanu-PF youth leader, said the demonstration was a "send-off" for Mugabe as he encouraged people to march to State House.
Activist pastor Evan Mawarire described the rally as "a momentous occasion" and an opportunity for a "fresh start" to advance democratic change.
Mawarire has faced charges of undermining the president and trying to overthrow an elected government for calling on Zimbabweans to protest against spiralling economic and political problems.
Marches have also been called for in parts of South Africa, the UK and the US - countries where millions of Zimbabweans migrated to in search of safety and better living, as various economic and political crises at home have left more than 70% living below the national poverty line.
Mugabe has 'lost control'
All 10 of Zanu-PF's provincial structures have passed a motion of no-confidence against Mugabe and called on him to step down as the ruling party's first secretary.
Zanu PF's 10 Provincial Coordinating Committees (PCC) said the leader had "lost control of the party and government business due to incapacitation stemming from his advanced age".
The provincial branches' move was carried by Zimbabwe's state broadcaster ZBC, which was seized by the army as part of its takeover on Wednesday.
If Mugabe fails to resign on Saturday, the party says it will convene a special committee meeting on Sunday in which the Zanu-PF Central Committee will consider the provincial resolutions to recall Mugabe.
The Zimbabwean president appeared in public on Friday - the first time since the army's takeover on Wednesday - attending a university graduation ceremony in Harare.
Zimbabwe's military has said it was engaging in talks with Mugabe, promising an outcome soon.
"[Mugabe] knows this not a game," independent parliamentarian Temba Mliswa told Al Jazeera.
As a legislator, he said he would start the process to put forward a motion to pass a vote of no confidence.
"If he refuses to leave we will start a motion to pass a vote of no confidence in his presidency when parliament sits again on Tuesday."
Regional dignitaries from the Southern African Development Community (SADC) are expected to meet on Sunday in an extraordinary session to discuss the Zimbabwe situation in neighbouring Botswana, where the SADC headquarters is located.
While the region's leaders have been silent on Mugabe's fate, Botswana's President Ian Khama has openly called for the elderly veteran to step down.