Ahmet Şık was detained on suspicion that he insulted the state, its military and police and engaged in terrorist propaganda on Twitter.
"I am being detained. I am going to be taken to the prosecutor's office over a tweet," Şık, the author of several books, said on Twitter.
Şık's books include notably one of the few full-scale investigations into the group of Fethullah Gülen, the US-based Islamic preacher who Ankara blames for the July 15 failed coup against President Recep Tayyip Erdoğan. The book, called "The Imam's Army" and published in 2011, examines how Gülen supporters infiltrated the Turkish bureaucracy and built up an alliance with the then-Prime Minister Erdoğan and his ruling AKP party that has now collapsed.
In 2011 he was jailed for a year over the book, as part of a series of court cases that led to the imprisonment of hundreds of soldiers and journalists who were targeted by the Erdoğan-Gülen alliance.
The convictions were later overturned and cases were thrown out.
