Three police officers in Kenya stood before a court Thursday after a serial killer vanished while they were on duty.

Masten Milimo Wanjala was arrested on July 14 over the disappearance of two children, but in a chilling confession, he admitted to killing at least 10 others over a five-year period.

"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 at the time, describing him as a "bloodthirsty vampire."

The 20-year-old was due for a court appearance Wednesday over the cold-blooded murders which targeted 12- and 13-year-old children when officers noticed he had disappeared during the morning roll call.

Three officers who were on duty at the Nairobi police station where he was held have since been arrested, said Augustine Nthumbi, the regional police commander.

"They are with the director of public prosecutions," Nthumbi told Agence France-Presse (AFP), adding that the search for Wanjala was ongoing.

The officers appeared before a Nairobi court Thursday but no charges were read to them.

Prosecutors have asked for the officers to be detained for 14 days to give them time to investigate allegations that they either aided or "neglected to prevent" Wanjala's escape.

The court is due to rule on that request on Friday.

The Independent Policing Oversight Authority (IPOA) watchdog announced on Thursday that it too was probing the escape.

Drained of blood

Police had in July described Wanjala's arrest as a major breakthrough in an investigation into a spate of disturbing child disappearances in the East African country where a significant number of children suffer from malnutrition.

His victims were drugged and drained of their blood and some of them strangled, police said.

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.

"Unbeknownst to some of the worried families, their children were long executed by the beast and their remains dumped in thickets. Others were submerged in sewer lines in the city and left to rot away," the DCI said in July.

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 (of) pleasure" from killing his victims.