Two sisters aged four and nine were on Wednesday evening defiled and then murdered at their guardian's home in Kenyanya village, Kisii County.
Reports indicated that Diana Kwamboka and her younger sister Stevan were had returned from school at about 2pm.
The older girl was in Grade 1 and the younger one in PP1 at Kenyenya Primary School.
The guardian, businesswoman Gladys Kerochi, left the girls at home at about 3pm and headed to the market..
It was while they were home alone that they were attacked.
Ms Kerochi's relatives said she and her husband Mason Kerochi, a teacher, had been taking care of the girls for about four years.
One was their grand child and the other their niece.
“They have three children who live outside Kisii so they brought the two girls to stay with them,” said James Ayubu.
Mr Kerochi, a teacher at Riokindo Primary School, told the Nation that his wife had a meal with the children before leaving to attend to her small business.
He said that when he went back home, he knocked the gate but there was no response yet the girls usually rushed to let him in.
Mr Kerochi then decided to jump over the fence.
He found the body of one of the girls a few metres away, with the blouse around the neck and no underwear.
He called the other girl but she did not respond and while searching for her, he found her body in the same condition in the kitchen.
“We suspect the assailants defiled the innocent girls before killing them after realising that they could expose them,” he said.
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.
Kenyenya Deputy County Commissioner David Mbevi said police arrested three suspects.
“One is a hardcore criminal who was recently released from jail. The other two were arrested because of proximity and for loitering in the area,” he said.
The bodies were taken to Hema Hospital mortuary.
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.