Two sisters aged between six and nine were on Wednesday evening defiled and then murdered in Kenyanya, Kisii County.
Reports indicated that they were home alone at the time of the incident as their mother had gone to a market.
Kisii County Police Commander Martin Kibet said the minors may have been murdered after identifying the attackers.
"We are investigating the incident. Habits that are injustices to humanity must come to an end," said Mr Kibet.
Cases of the defilement, and sometimes murder, of minors have been on the rise in several parts of the country.
On June 6, the body of a missing primary school pupil was found dumped in a maize plantation in Ndhiwa, Homa Bay County.
Police said the 15-year-old Kenya Certificate of Primary Education exams candidate was defiled before she was murdered.
One suspect was arrested.
In Narok East Sub-County June 11, a five-year-old girl was found dead shortly after she had been reported missing.
Preliminary investigations revealed she was defiled and then strangled; she sustained injuries to her private parts and neck.