The suspects, arrested in 25 provinces, include 12 soldiers -- both active duty and not -- and six civilians, said the sources, who asked not to be named due to restrictions on speaking to the media.
They are part of a group of 45 suspected members of the Fetullah Terrorist Organization (FETO) that Istanbul prosecutors issued arrest warrants for, including 25 soldiers and 20 civilians.
The warrants include 17 active-duty soldiers, three dismissed soldiers, three retired soldiers ,and two military cadets.
One of the arrested suspects, identified as a major with the initials M.E.T., is said to have been the Kastamonu central commander.
FETO and its U.S.-based leader Fetullah Gulen orchestrated the defeated coup of 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.