Isis declared its ambition to develop weapons of mass destruction in the most recent edition of its propaganda magazine Dabiq, and Indian defence officials have previously warned of the possibility the militants could acquire a nuclear weapon from Pakistan.

According to the Australian foreign minister, Julie Bishop, Nato has expressed deep concerns about the materials seized by Isis from research centres and hospitals that would normally only be available to governments.

The threat of Isis’s radioactive and biological weapons stockpile was so severe that the Australia Group, a 40-nation bloc dedicated to ending the use of chemical weapons, held a session on the subject at its summit in Perth last week.