More than a dozen Britons and a handful of Americans are among Islamic Statefighters reportedly named in a cache of 22,000 documents obtained by German intelligence.

Britons identified in the documents so far had previously been revealed to the public and are dead, killed in US-led strikes, or their whereabouts unknown. Sixteen Britons are thought to be on the list, among them Junaid Hussain and Reyaad Khan.

The documents, thought to be from a border crossing into Syria, are questionnaires of each would-be recruit. There are 23 questions, including names, date and place of birth, hometown, telephone number, education and blood type.

Germany’s interior minister, Thomas de Maizière, confirmed the documents were real and they would facilitate “speedier, clearer investigations and stricter prison sentences” for those returning from Syria and Iraq. De Maizière said the materials help clarify “the underlying structures of this terrorist organisation”.