A mass grave with at least 12 bodies, including that of a mother of five, was found in a thicket in Mandera county on Sunday.
It is believed the victims were among 59 people who have been reported missing in the county.
They are allegedly victims of what are suspected to be forced disappearances and extrajudicial killings by security agencies.
Of the 12, only the woman was identified – as Isnina, a tea vendor in Mandera town. Her freshly buried body was found naked, with broken bones and missing teeth, alluding to torture.
Isnina was was reportedly picked from her kiosk opposite Al-Furqan mosque last Wednesday by people in an unmarked Probox who identified themselves as police officers.
Witnesses who sought anonymity said two military vehicles followed the car.
The Kenya Defense Forces, Rapid Deployment Unit, Anti-Terror Police Unit and the National Intelligence Service have been accused of kidnapping and killing terror suspects.
Police spokesperson Charles Owino defended security agencies saying anyone with proof they were involved should present it.
“No one has reported anything to us. Let them officially report to us for forensic investigations to be carried out and victims identified,” he said.
“I can invoke my mother’s name in saying that we did not send any security officer to kill any innocent person.”
Mandera Senator Billow Kerrow said the killings are “utterly disgusting” and “a clear indication that this evil process of the extermination of suspects in total disregard of due process is the norm rather the exception”.
“This has clearly gone too far and must stop. It is time we said ‘no’, not just as leaders but also as a society,” he said, adding county leaders will meet to plan action.
Mbalambala MP Abdikadir Aden said those behind the killings must be identified and punished.
“We must get to the bottom of these mass graves. You are right, it is likely the work of extrajudicial killings. Very sad,” he said.
A mass grave with at least 11 bodies was found in Wajir in May. The victims have neither been identified nor the motive for their killings established.