In the Samsun-based operation, the counter-terrorism police conducted raids in capital Ankara, Samsun, Istanbul, Van, Izmir, Bitlis, Erzurum, Kayseri, Diyarbakir, Hakkari, Bursa, Adiyaman and Tunceli provinces, said the sources, who asked not to be named due to restrictions on speaking to the media.
The operation continued to nab one more suspect, they added.
FETO and its U.S.-based leader Fetullah Gulen orchestrated the defeated coup on July 15, 2016, which left 251 people martyred and nearly 2,200 injured.
Ankara also accuses FETO of being behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police, and judiciary.
