NAIROBI, Nov 13 (Reuters) - Kenyan police said on Thursday they had rescued an 18-year-old boy who was forced by his stepmother to sleep in a chicken coop for the past 10 years.

Investigators acting on a tip-off found James Kimathi Mwirigi badly malnourished and scarred from apparent beatings in the central Kenyan district of Meru, a police official said.

"His stepbrother confirmed to us that he has been maltreated. But he is above the age of what is considered a child, so we have to proceed very carefully," the commanding police officer told Reuters.

Villagers told police that the teenager -- thought to be mentally disabled -- was denied food and a proper education, while being made to carry out household duties and farm chores.

According to neighbours, the stepmother had a reputation for cruelty and was shunned in the village. Police said they were searching for the parents.