The Investigative Committee said the body of a child aged three or four years with "signs of violent death" had been found earlier today in an apartment in northwest Moscow after a fire was extinguished there.
"According to preliminary information, the child's nanny -- a native of one of the Central Asian countries, born in 1977 -- waited until the parents left the apartment with their elder child and, guided by unknown motives, killed the little one, set the apartment on fire and left the scene," the Investigative Committee said in a statement.
Investigators said the woman was detained and a criminal probe opened. They said the suspect would undergo a psychiatric examination to establish whether she "understands the meaning of her actions and behaviour."
The Investigative Committee did not provide further comments.
Interfax news agency, citing a law enforcement source, identified the woman as 38-year-old Gyulchekhra Bobokulova, a native of ex-Soviet majority-Muslim Uzbekistan.
Interfax said she was detained near a metro station in northwest Moscow with the child's head.
Russia's interior ministry declined to comment.
