A British man in Syria has told the BBC why he is fighting for a group linked to al-Qaeda.
Ifthekar Jaman, 23, from Southsea, Hampshire, told Newsnight the Islamic State in Iraq and the Levant (ISIS) was engaged in a jihad to establish a state based on Islamic religious law.
He said it was his "duty" because Muslims were "being slaughtered".
Mr Jaman, whose family come from Bangladesh, is believed to have left the UK in spring of this year.
His exact location inside Syria is unclear. Newsnight managed to speak to him via an internet video call, with the help of his brother in the UK.