Human Rights Defenders Robson Chere, Namatai Kwekweza and Samuel Gwenzi have been denied bail by Magistrate Ruth Moyo.
The three were arrested on July 31 while aboard a plane to Victoria Falls.
They are charged with disorderly conduct and are accused of staging a protest at the Harare Magistrates Court demanding the release of jailed Citizens Coalition for Change (CCC) interim leader Jameson Timba and opposition activists.
Moyo denied the three bail ruling that they are likely to reoffend.
She said the three evaded arrest which justifies their continued detention.
"Having taken into account that some of their accomplices escaped they might regroup and reoffend," she said.
Moyo said the State gave sufficient grounds for the three to remain in custody awaiting trial.