A British medical student, who left the UK to join terrorist organisation Isis, has posted an image of herself on social media brandishing a severed head.
The woman, who goes by the Twitter name of Mujahidah Bint Usama, claims to be a doctor for the terror group based in Raqqa, Syria.
In the image, she is seen wearing a full burka with a white lab coat, while holding the head of a man. Two children can be seen standing beside her watching.
Alongside the image is the chilling message "Dream job, a terrorist doc," followed by a series of smiley faces and love hearts.
Bint Usama, who takes her name from mujahadid - meaning soldier of God, has more than 800 followers on the social media site. She has previously tweeted images of dead soldiers and the 9/11 terror attacks, alongside information on how to treat an injured knee and insomnia.
In other online messages, Bint Usama praised Anwar al-Awlaki, an extremist Yemeni preacher who became an al-Qaida spokesman and who is believed to have inspired hundreds of Western jihadis to take up the cause.
She also urged women to push their husbands into fighting for Islam, and shared images of the execution of US journalist Steven Sotloff, who was beheaded by Isis earlier this month.
She has been linked through her Twitter account to the al-Khanssaa brigade, a female-only militia of jihadists, who are charged with punishing 'un-Islamic' behaviour by women in Raqqa.
The al-Khanssaa brigade was set up by Aqsa Mahmood, 20, of Glasgow, who fled to the country last year. The brigade comprises British extremists who are believed to have been acting as madams running brothels filled with captured Yazidi women.
As many as 3,000 women and girls have been taken captive from the Yazidi tribe in Iraq, as Isis militants continue their reign of terror across the region.
The think tank MEMRI (the Middle East Media Research Institution) released a report saying that IS had taken many Yazidi women to be sold and used as sex slaves.
It is believed that US hostages James Foley and Steven Sotloff were both beheaded in the desert near Raqqa and it is likely that the British women in al-Khanssaa could know who killed them.
Academics at King's College London have identified three other British females as members of the group and claim there are about 60 UK women who have gone to Syria on jihad.
GCHQ and MI5 are known to be monitoring the accounts of around 60 female British jihadis who are believed to be in Raqqa in order to put together a picture of their activities.
The government has previously stated that those who take part in atrocities such as beheadings and massacres will be prosecuted for war crimes and terror offences if they return to the UK.