British medical student who joined IS poses with severed human head.

A woman thought to be a UK medical student who left Britain to join the Islamic State has posted a Twitter selfie of her holding a severed head.

Claiming to be a doctor with the terrorist group in their stronghold of Raqqa, Syria, the woman can be seen in a white lab coat and full burka holding up the head of a middle-aged man.

The woman, using the Twitter name Mujahidah Bint Usama, added the photo as her profile picture alongside the message “Dream job, a terrorist doc”.

It has since been removed from Twitter.

The social media post came as a third westerner was beheaded by the Islamic State. The group released footage of the killing of British aid worker David Haines.

Britain’s Sunday Telegraph reported that the woman is a 21-year-old British medical student although it didn’t give a name.

The woman has reportedly been linked through her Twitter account to the al-Khanssaa brigade, an all-female militia set up by the Islamic State in Raqqa who police un-Islamic behaviour among women in the city.

British intelligence services are thought to be monitoring the accounts of around 60 female British jihadis who are believed to be in Raqqa.