Kenya's law society has demanded the authorities reveal the whereabouts of lawyer Willie Kimani, who has been missing for a week.
It believes he was abducted by "rogue elements within the police" after leaving court in the capital, Nairobi, last Thursday.
Mr Kimani was representing a client making a complaint against the police.
The law society says this is the first time that a lawyer working on a sensitive case has gone missing.
Police have not yet commented on Mr Kimani's disappearance.
His client and the driver of their taxi are also missing.
The case concerned allegedly false charges against the client after he accused the police of accidentally shooting him, the New York Times reports.
Mr Kimani was working for a US legal charity, the International Justice Mission, which focuses on cases of police abuse of power.
In a statement it said: "We are heartbroken by this horrific crime and are doing everything we can to locate these men and support the families of the victims."
Law society president Isaac Okero told the BBC's Mohammud Ali in Nairobi that the incident suggests "lawyers are becoming a target because of their work".
"This is an indication that the rule of law is beginning to crumble," he added.
The society says that the police are now investigating what happened to Mr Kimani and the other two men.