The veterans of the 1970s liberation war, known for their loyalty to Mugabe, are divided over who should succeed the 91-year-old leader.
Police dispersed a faction that had gathered in a sports centre in Harare before a planned march to the headquarters of Mugabe's ruling ZANU-PF party in the city.
The group wanted to voice their anger at the ongoing divisions in the debate about Mugabe's succession.
Police have in the past allowed protests by the once-formidable force that fought in the country's liberation war in the 1970s.
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ZANU-PF is riven by factional fights between two main groups, one named G-40, made up of supporters under the age of 40 aligned to Mugabe's wife Grace, and another section loyal to vice-president Emmerson Mnangagwa.
Mnangagwa has long been seen as Mugabe's heir, while Grace 50, who was appointed leader of the powerful ZANU-PF women's wing in 2014, has also shown political ambitions.
Mugabe, who has ruled since independence in 1980 and turns 92 on Sunday, has avoided naming a successor, at one point saying there was no one in his party fit to succeed him.