The case has added to doubts over implementation of a power-sharing agreement between President Mugabe and opposition leader Morgan Tsvangirai, seen as a chance of rescuing the once relatively prosperous country from economic collapse.
Hyper-inflation means prices double every day and a cholera epidemic has killed nearly 1,200 people.
Reports of violence
Mukoko's independent organisation monitored human rights and had compiled reports of violence at elections this year that were widely condemned outside Zimbabwe.
The state-run Herald newspaper said the activists were accused of recruiting or attempting to recruit people for military training to topple the government.
|Mugabe has rejected growing international calls for him to step down from power [EPA]
Citing a police statement, it said some of the activists had recruited people for training in Botswana, including a police constable.
It said the plan was to "forcibly depose" Mugabe's government and replace it with one headed by Tsvangirai.
The opposition says abductions of activists have continued since a June presidential election run-off in which Mugabe was re-elected unopposed after Tsvangirai withdrew, complaining of attacks on his supporters.
Tsvangirai has threatened to suspend negotiations on a September 15 power-sharing agreement if arrests do not stop. He won a first round election in March, but without an absolute majority.
Talks on sharing power have been deadlocked over control of key ministries, pushing Zimbabwe deeper into crisis.
The court appearance of the rights activists came a day after Mugabe told George Bush, the US president, to stay out of his country's political affairs, calling him a "dying horse".
The White House earlier announced that it could no longer support a government that includes Mugabe.
"The inclusive government does not include Mr Bush and his administration. It doesn't even know him," Mugabe said in a speech at a funeral ceremony for an official from his ruling Zanu-PF party.
"It has no relationship with him, so let him keep his comments, they are undesired, irrelevant, quite stupid and foolish.
"We realise these are the last kicks of a dying horse. We obviously are not going to pay attention."
'Out of touch'
On Sunday Jendayi Frazer, the US assistant secretary of state for African affairs, accused Mugabe of reneging on the power-sharing pact with Tsvangirai.
Frazer said he was "completely out of touch". She also said he was responsbile for turning the once prosperous country into a "failed state".
But despite mounting criticism of his rule, there is little that Western powers can do to force Mugabe out.
Sanctions have failed to weaken him and analysts say that military intervention in unlikely because Zimbabwe is not seen as a strategic country with key resources such as oil.