Opposition is mounting against the 92-year-old Mugabe, whose decades in office have been marked by economic decline, repression of dissent, claims of vote-rigging, mass unemployment and emigration.
"Some were arrested last night. Some, earlier," lawyer Obey Shava told AFP.
"The charges are robbery and obstructing or defeating the course of justice."
Shava said police rounded up the activists while they were holding a vigil in Africa Unity Square in central Harare calling upon Mugabe, in power since 1980, to step down.
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"These are trumped up charges to instil fear and discourage people from occupying Africa Unity Square," the lawyer said.
The square has been the venue of a series of protests over the disappearance of political activist Itai Dzamara who was abducted in March last year, allegedly by military intelligence agents.
His brother Patson, who was among those arrested, last week released a picture he said showed the missing man being held at an undisclosed location.
The army has denied responsibility for Dzamara's abduction.
The journalist arrested at the protest was Paidamoyo Muzulu of NewsDay.
"There is a clear indication and consensus that President Robert Mugabe has failed us. We feel very strongly that he too old to continue," the convenor of the meeting, Pastor Ancelimo Magaya, told local media.