A woman dressed all in black and holding what is thought to be a child’s severed head has been arrested near a metro station in Moscow. Picture: Twitter

RUSSIAN police have arrested a nanny for beheading a young girl in her care, investigators said.

Local media is reporting the Burqa-clad woman was arrested on Monday while carrying the child’s severed head outside a metro station in Moscow.

The Investigative Committee said the body of a child aged three or four years with “signs of violent death” had been found earlier on Monday 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.

The victim is said to have had learning difficulties and could not walk.

The woman was shouting, “I am a terrorist,” and reportedly threatened to blow herself up.Source:Supplied

A woman has been arrested outside a Moscow metro station after she was seen to be holding the severed head of a child.Source:Supplied

State news agency TASS, citing a source, said: “The child’s body was without the head. According to a preliminary version, the nanny carried away the head.”

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.”

Gruesome video shows the woman outside Oktyabrskoye Pole underground station holding the head in her hands while shouting “Allahu Akbar,” Arabic for “God is great”.

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.

The parents told police the nanny had been working for them for 18 months and a source told Interfax that she was “drugged”.

LifeNews, a news service known for its close ties to law enforcement agencies, said that when local police approached her for a document check she responded by taking the head out of a plastic bag and started shouting that she had killed the child.

Eye-witnesses claimed the woman was threatening to blow herself up at the scene but police said no explosives were found on her.

The mother of the child, who works nearby in a wedding shop, is said to have collapsed upon hearing the news and remains unconscious in hospital.

Russia’s interior ministry declined to comment.

The woman appeared near Oktyabrskoye Pole metro station in northwest Moscow.Source:Supplied

Russian news agencies report that police have arrested a woman who was waving the severed head of a small child outside a Moscow subway station. Picture: Alexander ZemlianichenkoSource:AP

Russian police officers secure the area near a subway station in Moscow on Monday, Feb. 29, 2016. Picture: Alexander ZemlianichenkoSource:AP