Dozens of doctors marched at Zimbabwe's biggest hospital on Sunday, demanding the release of a union boss believed to be abducted after calling for a pay strike.
Several government critics, including a comedian and a teachers' union leader, have in recent weeks been abducted from their homes, tortured and warned by suspected state security agents to back off from anti-government actions.
The Zimbabwe Hospital Doctors Association (ZHDA) says their president, Peter Magombeyi, was abducted on Saturday, just days after he received threats on his phone.
His Vice President, Masimba Ndoro, said Magombeyi had alerted colleagues that three unidentified men were forcibly taking him away.
Senior ZHDA member Tapiwa Mungofa lead protesters in chants, saying: "No Peter, no work, we will not go back to work."
The association represents hundreds of newly-qualified doctors who are doing their residencies.
The doctors, who earn less than $40 a month, want a review of their salaries and allowances.
Magombeyi had expressed concerns to journalists about the poor state of Zimbabwe's hospitals.
Police spokesman Paul Nyathi says he has yet to receive details of the case.