Kenyan police were holding a man described as a "bloodthirsty vampire" accused of the grisly murders of at least 10 children, AFP reported.
Masten Milimo Wanjala was arrested over the disappearance of two children but in a chilling confession, admitted to killing many more, police said.
The 20-year-old took officers to the site where he had dumped their bodies in a forested area of the capital, and confessed to the cold-blooded killing of at least 10 young teenagers, they said.
Police described his arrest as a major breakthrough in an investigation into a spate of disturbing child disappearances in Kenya—almost two a day in recent weeks, according to police data.
"Wanjala single-handedly massacred his victims in the most callous manner, sometimes through sucking blood from their veins before executing them," the Directorate of Criminal Investigations (DCI) said on Twitter, describing him as a "bloodthirsty vampire."
The murders, targeting 12- and 13-year-olds, stretch back five years. His victims were drugged and drained of their blood and some of them strangled, police said.
Such cases of kidnappings involving school-going children, some ending up dead, have become rife in recent months and sent parents panicking.
According to police, Wanjala's first victim was a 12-year-old girl he kidnapped five years ago in Machakos county east of Nairobi.
The murder of his next victim in western Kenya sparked protests, with locals torching the house of the person they suspected killed the boy.
The bodies of several children feared to have died at Wanjala's hands have yet to be found.
Wanjala was unapologetic over his actions and told detectives he derived "a lot pleasure" from killing his victims.