A nanny detained by police while holding the severed head of a 4-year-old girl told a Moscow court on Wednesday that "Allah commanded" her to kill the child, the Interfax news agency reported.
The woman, 38-year-old Uzbek national Gulchehra Bobokulova, is a diagnosed schizophrenic, the report said.
The court approved Bobokulova's arrest and remanded her to custody for two months while authorities build their case.
Authorities said Bobokulova might have been manipulated into committing the crime by individuals who were still at large.
Bobokulova was caught waving around the baby's severed head on Monday near a metro station in north-west Moscow.
Clad in a black burka, the woman yelled "Allahu Akbar" (Allah is great) before being captured by police.
Authorities found the rest of the baby's body in the family's burned-out apartment after extinguishing a blaze that Bobokulova is believed to have started.
Muscovites have been laying flowers and children's toys outside the metro station October Field, where Bobokulova was detained.