Escorted by armed police, handcuffed Gyulchekhra Bobokulova - herself a mother of three - showed officers the Moscow flat where she apparently strangled Nastya Meshcheryakova, who had learning difficulties, before cutting off her head with a kitchen knife. The little girl’s remains were left in her cot.

The 38-year-old nanny told police she was haunted by 'voices' on the day of the murder, and was driven mad with anger after discovering that her husband in Uzbekistan had started a new family while she was away working in Russia. She claimed she had refused his offer to become his second wife.

In scenes that shocked the world yesterday, the hijab-wearing nanny was seen walking the streets of Moscow brandishing the head of the dead girl for an hour before she was detained by police. 
Reports suggest she had become enraged after learning of her husband's infidelity. 

But another theory has surfaced in Russia which suggests she was angered by a Tajik boyfriend who she had met in Moscow.

A source said: 'All of a sudden she found out that he was actually married. It was a shock for her. She came back to Moscow in shock.' 

Bobokulova is believed to be co-operating with investigators and showed how she killed the child, with sources saying she strangled the girl before using a kitchen knife to behead her.

She shouted 'I am a terrorist' and threatened to cause an explosion but, despite the FSB security service leading the probe, the Russians so far have no evidence of a link to extremist groupings.

Bobokulova was taken to the flat in western Moscow at around midnight - only 16 hours after the appalling killing to which - say police sources - she has confessed.

The parents were being comforted by friends and relatives after their daughter's horrific death. Nastya - or Anastasia - had special needs after problems during her birth.

The nanny 'cared for her like her own child', according to one source.

The beheaded remains of the four-year-old were found in a cot in the family flat, dressed in her night clothes, a T-short and shorts. On her blanket was a picture of a kitten.

The Kremlin backed decisions by Russian media organisations not to show gruesome pictures of the crime scene inside the flat.