Germany's interior minister has said stolen files detailing hundreds of recruits to the Islamic State militant group can be assumed to be genuine.
Thomas de Maiziere said the information could help with prosecutions of IS fighters, and help prevent future recruitment to the militant group.
Files obtained by German, UK and Syrian opposition media are said to identify IS recruits from at least 40 countries.
Some 22,000 names appear to be listed but most may be duplicates.
Names, addresses, phone numbers and skill sets are listed on official-looking forms.
Files were published online (documents in Arabic) by Zaman Al-Wasl, a Qatari-based Syrian news website:
- Two of those listed, Kerim Marc B and Abdelkarim B, are currently on trial separately in Germany, while another two Germans on the list, Farid Saal Yassin Oussaiffi, have appeared in IS videos
- Dutch media identified Abu Jihad al-Hollandi as Amsterdam teenager Achraf Bouamran, killed in a US air strike on the Syrian IS stronghold of Raqqa in January 2015. His file reads: "Born 1997. Moroccan origin. Wants to be a fighter"
- Sixteen Britons including two killed in air strikes in Syria, Junaid Hussain and Reyaad Khan, also reportedly feature in the files
One file refers to a German recruit who used to be "in sales" and now "wants to be a suicide bomber", while another would-be suicide bomber (nationality not given) formerly worked as a "tobacconist in a restaurant".
Another mentions an Australian who was willing to "martyr" himself, but the document expressed concerns over his night vision, and inability to drive a car with manual gear change, CNN reports.
Counter-terrorism police in Germany are studying the documents.
"The German Federal Bureau of Investigation acts on the assumption that the documents are authentic," Mr de Maiziere said.
"We can also improve our understanding of the structures of this terror organisation," he added. "And possibly, it will discourage young, radicalised people, who believe they are doing something good if they become a member of a criminal organisation."
His counterpart in the UK, Home Secretary Theresa May, said she could not comment on "specific national security matters".
IS "poses a severe threat... it is important for us to work together to counter this threat", she added.
'Stolen memory stick'
Sky News said the files contained 22,000 names, addresses, telephone numbers and family contacts of jihadists.
It said the documents came from a man called Abu Hamed, an IS fighter who said he had become disillusioned with the group's leadership and stolen a memory stick from the head of the IS internal security force before handing it over in Turkey.
Stefan Kornelius, foreign editor of Germany's Sueddeutsche Zeitung newspaper, told the BBC the paper had obtained the documents from a "trusted source".
"It gives some proof on the state of Isis [IS] right now, since many of those members and those being close to the terrorist group are trying to make money, quite honestly, because obviously the Isis is in a desperate financial state," he said.
Snapshot of jihad: Analysis by Gordon Corera, BBC security correspondent
What appears to be a personnel database for the group could be of real intelligence value for Western security services - if it proves authentic.
The data looks to be a snapshot from late 2013 or early 2014, so will not be current but still could have its uses. It would help the authorities check that they had not missed anyone who had travelled to join IS.
The section saying who had recommended an applicant and how they had travelled out could also be useful in tracing networks and connections.
British authorities will not comment on whether they have the database but the Germans (who also seem to have received it from a media organisation in their country) are also suggesting it could be useful as evidence in prosecuting those who return.
Some of the papers are stamped Islamic State in Iraq and the Levant, which pre-dates the rebranding to Islamic State in June 2014.
Analysts say IS is known to be bureaucratic, so such lists may not be surprising.
Zaman Al-Wasl published the details of 1,736 IS members, based on leaked data it first reported in January.
It said the files contained 22,000 names but most had turned out to be duplicates. It was not immediately clear if the website's data matched the files obtained by German and UK media.
Shashank Joshi, a senior research fellow at the Royal United Services Institute think-tank, told the Press Association the papers could be "incredibly important".
He said: "It is a law enforcement gold mine. It means it might make it easier to prosecute those who have returned."
IS, a fundamentalist Sunni Muslim group, is notorious for its brutal methods in gaining territory in Iraq and Syria.
Are the documents genuine? Analysis by BBC Monitoring jihadist media expert
Some analysts have raised questions about the authenticity of the documents, noting inconsistencies in language and other oddities in the recruitment questionnaires such as:
- The old name for IS - Islamic State in Iraq and the Levant (Isil) - is rendered in two slightly different ways on the documents
- An unusual logo is used at the bottom saying "Islamic State is here to stay"
- The questionnaire has a section for recording when and where a fighter was "killed" rather than "martyred" - jihadists' preferred terminology
But none of that is conclusive. The documents were clearly not intended for public consumption, so those who drafted the questionnaire may not have paid as much attention to detail as for public documents.
And they should be compared not with IS documents of today, but of around two years ago, when they appear to originate - before the group's rapid land grab across northern Iraq and Syria, when its bureaucracy and administrative capabilities were less well developed.