A mobile phone containing vital information on Islamic State (Isis; IS) was found concealed in the rectum of a captured suspected extremist, Turkish authorities said.
Yasser Mohammed Salem Radown, also known by a jihadist moniker 'Abu Jihad', was captured in a police raid in Istanbul in the wake of the New Year's attack on the city's Reina nightclub, which killed 39 people.
Police recovered the telephone from the man after his arrest, containing information on the extremist's activities and pictures of weapons, Turkey's Hurriyet Daily News reported.
The man was an alleged 'judge' in IS-controlled areas within Syria and Iraq, and sought to impose the group's brutal interpretation of Sharia law.
A notebook, containing the names, addresses and telephone numbers of other suspected supporters of the group was also recovered in the raid, a court heard.
A judge ordered the formal arrest of the man, whose nationality and age were not given, according to the report.
The chief suspect in the nightclub attack, Abdulkadir Masharipov, was arrested in Istanbul last week.
After his arrest, Turkish authorities described Uzbekistan-born Masharipov, 34, as "very well trained". Officials believe he trained as a militant both in Afghanistan and Pakistan and has contacts inside Syria with IS.
Police in Turkey are hunting for suspected accomplices of Masharipov.
In the last year IS has launched a series of attacks in Turkey, including a gun attack on Istanbul's Ataturk Airport in June in which 45 people were killed.