A nanny accused of decapitating a young girl in her care then walking through the street brandishing the head, on Wednesday said "Allah ordered" the killing as she appeared at a Moscow court.

Suspect Gyulchekhra Bobokulova from Muslim-majority Uzbekistan - whom the press have dubbed "the bloody nanny" - was detained on Monday as she was waving the child's severed head outside a Moscow metro station. She was sent for psychiatric examinations.

"It was what Allah ordered," the 38-year-old told journalists as she was brought into the district court to have her arrest confirmed and extended.

"Hi to everyone," said the mother-of-three, waving at the crowd of journalists in the courtroom.

Investigator Olga Lapteva, who was clearly emotional, told the court that Bobokulova was suspected of committing an "extremely serious crime" and that she should face "a mandatory prison sentence of considerably more than three years."

The court confirmed the nanny's arrest and ordered her held in custody for two months as investigations continued.

Investigators said they were still trying to establish if Bobokulova had any accomplices.

Bobokulova has been undergoing psychiatric examinations since her detention over the murder of the girl, Nastya, whom the judge said was born in 2011. Investigators had initially estimated she was three or four years old.

She is suspected of butchering the girl, who had suffered from learning disabilities and epilepsy, at the family's apartment in northwestern Moscow, before torching it and fleeing the scene.

'Too monstrous for TV'  

Witnesses reported seeing an agitated woman dressed in black who threatened to "blow everyone up" with one media report saying she shouted "Allahu Akbar" as she paced up and down outside a metro station.

The shocking incident has shaken usually hard-bitten Muscovites and people have flocked to the Oktyabrskoe Pole metro station to lay flowers and pray.

Russia's national television channels have, however, refused to cover the killing in a controversial move that the Kremlin defended as the subject was "probably too monstrous to be shown on television".

Many have questioned the professionalism of police after Bobokulova was allowed to pace up and down outside the metro station with the head for about 20 minutes.

A spokeswoman for the Office of the General Prosecutor said a probe would be launched into the matter.

The mass-circulation Moskovsky Komsomolets, citing Uzbek police, said the woman had suffered from schizophrenia for about 15 years.

Komsomolskaya Pravda, citing a close family friend, said the live-in nanny had recently become very religious, spent a lot of time online and had brought home a prayer mat.