Turkish police on Tuesday detained dozens of people, including former military personnel, for alleged links to the Gülenist Terror Group (FETÖ), security sources said.

An Istanbul-based operation in 40 provinces was launched early Tuesday to detain 144 military personnel, the sources said on condition of anonymity.

"A total of 20 suspects have been arrested so far," the sources added.

Tuesday's police raid was part of an ongoing investigation by Istanbul Public Prosecutor's office against suspected FETÖ members in the Turkish Armed Forces.

FETÖ, led by U.S.-based Fetullah Gülen, is accused of orchestrating the deadly July 15 coup attempt last year.

The failed putsch killed a total of 250 people and left more than 2,200 others injured.

Meanwhile, Ankara police have launched an anti-FETÖ raid across six provinces to detain 124 people including 36 former employees of the Capital Markets Board (SPK), 33 ex-personnel from the Information Technology and Communication Board (BTK) and 55 administrators of FETÖ-linked private schools, which were shut down by cabinet decree.

The suspects are accused of using the ByLock messenger app, a piece of encrypted smartphone software used by FETÖ members to communicate.

The operation saw the detention of 30 suspected FETÖ members from private schools; police are searching for the remaining suspects.

Moreover, 10 former police officers were detained in a separate operation in the central Anatolian province of Konya for their suspected links to FETÖ.

According to Konya Public Prosecutor's office, which has been operating the investigation, the suspects used the ByLock messenger app.

In another operation on Tuesday morning, 12 FETÖ suspects from the different professions were detained on similar charges in the central Aegean province of Uşak.

Two people were also detained from the western Turkish province of Kırklareli for using ByLock.