At least 17 children died after a fire ripped through their primary school dormitory overnight in central Kenya, police said Friday.

The blaze in Nyeri County's Hillside Endarasha Academy broke out at around midnight, police said, engulfing rooms where the children were sleeping.

The primary school caters to some 800 pupils, aged between roughly five and 12.

"There are 17 fatalities from this incident and there are also others who were taken to hospital with serious injuries," national police spokesperson Resila Onyango told reporters.

"The bodies recovered at the scene were burnt beyond recognition," she said.

Police said the average age of the victims was around nine years old.

Several others were injured, Onyango said, 16 of them seriously, and had been rushed to a nearby hospital.

"More bodies are likely to be recovered once [the] scene is fully processed," she said.

The cause of the fire remains unknown, she said, but an investigation had been launched.

Kenyan President William Ruto expressed his condolences.

"Our thoughts are with the families of the children who have lost their lives in the fire tragedy," he said in a post on X.

"This is devastating news."

He said he had instructed officials to "thoroughly investigate this horrific incident", and promised that those responsible will be "held to account".

The school is located around 170 kilometres north of the capital Nairobi. (AFP)