By Andrew Osborn
MOSCOW (Reuters) - Russian police wrestled to the ground a woman in a hijab brandishing the severed head of a child outside a Moscow metro station on Monday and charged her with murder, in an incident that stirred fears of an Islamist terrorist attack.
The macabre episode was caught on camera by passers-by, with footage showing the unnamed woman in a black hijab wandering around in the street holding an infant's severed head high in the air.
"I am a terrorist, I want your death," she can be heard screaming in heavily accented Russian in a rambling tirade in which she appears to criticize democracy and talk about the end of the world.
Investigators said they thought the woman had been working as a nanny for a Moscow family and had murdered a child in her care before setting fire to the family's flat and fleeing.
The child was three or four years old, they said.
"Given the clearly deranged behavior of the detainee, investigators swiftly ordered her to undergo psychiatric tests to establish whether she is capable of understanding the significance of her actions," Moscow's investigative committee said in a statement.
News agencies cited an unnamed police source as saying the woman appeared to have been under the influence of psychotropic drugs.
Immigration authorities told media the woman was from the former Soviet republic of Uzbekistan and had been working in Moscow illegally.
With frequent warnings from government officials about the danger that Islamic State militants pose to Russia and a long history of terrorist attacks in Moscow, some onlookers thought they were witnessing an act of terror.
One eyewitness, a reporter from the RBC.ru news portal, said she heard the woman screaming "Allahu Akbar" (Islamic phrase meaning God is Great or Allah is Greater).
"I was on my way to the metro station from home," Polina Nikolskaya, the reporter, told Reuters.
"She was standing near the metro entrance and caught my attention because she was screaming Allahu Akbar. I saw that she had a bloodied head in her arms, but I thought it was not real. People in the crowd said it was real."
Lifenews.ru, an online news portal with close contacts to the police, said a policeman had first approached the woman to check her documents near the Oktyabrskoye Pole metro station in the north-west of the Russian capital.
The woman had responded by removing the child's head from a bag and shouting that she had killed the infant, it said, saying she had also threatened to blow herself up.
Footage of the incident showed a policeman wrestling the woman to the ground before a group of colleagues helped restrain her.
Some rights activists warned of a possible backlash against migrant workers from Central Asia who have in the past been targeted for beatings by far-right groups.
Security services are on high alert for a possible terrorist attack after a Russian passenger plane was blown out of the sky above Egypt in October, killing all 224 people onboard. Islamic State said it was responsible and had acted to avenge the Kremlin's decision to launch air strikes in Syria.
(Additional reporting by Maria Tsvetkova; Editing by Hugh Lawson)