Media reports said that veterans of the independence war, activists and ruling party leaders have publicly called for Mugabe's exit and exile. Eight of Mugabe's ruling party's 10 regional branches have appeared on state television and called for him to go.
The 93-year-old autocrat is yet to resign and was said to be "buying time" to negotiate an end to his 37 year reign.
Saturday's marches will cap an unprecedented week in which army generals led by General Constantino Chiwenga seized power and placed Mugabe under house arrest.
On Friday, President Mugabe a attended a graduation ceremony.
Support is reportedly building up for ousted Vice President Emmerson Mnangagwa, whose sacking sparked the army intervention on Tuesday.
Pastor Evan Mawarire, an outspoken Mugabe critic who rose to prominence last year with his #ThisFlag protest movement challenging the president over the economic crisis, called on Zimbabweans of all backgrounds to march with the war veterans.
"The citizens are joining hands across political divides... across ideological divides," he said in a live broadcast on Facebook.
"We have joined hands with war veterans, with the church and young people. We will stand together for a new Zimbabwe... We are marching in order for us to thank our military."
Zimbabwe's military chiefs said in statement Friday they had detained some "criminals" in Mugabe's government after their lightning power grab which appeared to be the climax of a dispute over who would succeed the veteran leader. They did not give any indication about whether Mugabe would remain head of state. (ANI)