"A total of 24 people are dead as we speak but we are not able to tell who is Mungiki and who is not," Kiraithe said.
"At night, the groups of locals started attacking some of the youths they suspected to be Mungiki members and slashed some of them to death."
The violence prompted several residents to flee the area.
Police said the violence was linked to Mungiki members forcing people out of one district of Karatina, a town in the Nyeri West district of central Kenya, about 100km from the capital.
At least 15 suspected Mungiki members were hacked, stoned or burned to death by mobs in the area over the past 10 days.
"Residents of the two divisions in Kirinyaga and Karatina appear to be tired of these illegal groupings and their activities," Kiraithe said.
The Mungiki, which emerged in the 1990s, claims to have two million members in central Kenya and in the Rift Valley provinces and says it advocates a return to tribal traditions and customs.
But the authorities have accused the group of being a "mafia" involved in extortion, racketeering, protection rings, kidnapping and murder.
The group was banned in 2002.
Most of its members are from the Kikuyu, Kenya's largest ethnic group, and are said to have links to politicians and powerful families.
Two years ago, police allegedly killed hundreds of its members in a crackdown in Nairobi.