Haki Africa has expressed concerns following increased cases of criminal gangs in Mombasa.
The human rights group said the county is no longer safer "and it is leading with ruthless criminal gangs."
Haki Africa said the juveniles gang are armed with machetes, swords and spokes.
"The gangsters, most of them juvenile, carry machetes, knives and crude weapons and are under the influence of drugs."
They target women, children and security agents and kill at the slightest provocation, according to the rights group.
In a communication on Tuesday, Haki Africa said Mombasa security agents were grappling with re-emerging crimes by more than 200 juvenile gang members in Likoni and Kisauni.
The gangs have left residents in fear as they attack frequently despite police warnings and assurances that they have been contained.
"Most of them have dropped out of school and are hooked on drugs. They are young and dangerous."
On March 10, 22-year-old Salim M. Salim was attacked by a gang in Mlaleo who inflicted serious body injuries on him by a criminal gang in Kisauni. The victim was taken to Coast general hospital for treatment.
"HAKI Africa is condemning the escalating violence and general insecurity and is now call upon the national and county governments to restore normalcy in Mombasa," said the organisation after some of its officials visited Salim, on Tuesday.