Police have so far detained 40 people after Istanbul prosecutors issued warrants for 145 suspects, including military officers, said the source, who asked not to be named due to restrictions on talking to the media.
The Istanbul-based operation is ongoing across 22 provinces to apprehend the remaining suspects, the source added.
The suspects have been accused of being members of an armed terrorist organization, as well as alleged use of the ByLock mobile app, a suspected means of communication for FETO members.
Meanwhile, an Ankara court has accepted the indictment of over 220 FETO suspects, including alleged members of the so-called Peace at Home Council, thought to be an executive body that led the July 15 coup attempt in Turkey.
FETO, led by U.S.-based Fetullah Gulen, has been accused of orchestrating the defeated coup of July 2016 that left at least 249 people martyred, and around 2,200 others wounded.
Turkey's government accuses the FETO terror network of staging the coup attempt as well as being behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police, and judiciary.
Since the foiled coup, operations have been ongoing in the military, police and judiciary, as well as in state institutions across the country, to arrest suspects with alleged links to FETO.