KONYA, Turkey

A Turkish court has remanded in custody 21 army pilots Tuesday as part of an anti-terror investigation into the Fetullah Terrorist Organization (FETO), security sources said.

The Konya chief public prosecutor had issued arrest warrants for 73 pilots -- 71 lieutenants and two colonels -- last Thursday for their suspected links to FETO.

Since them, 66 pilots have been taken into custody. However, 16 have been released under judicial supervision.

A provincial security source, who spoke on condition of anonymity due to restrictions on talking to media, told Anadolu Agency that the arrests occurred in 17 provinces across the country.

The operation to arrest the suspects is still underway, the sources added.

Led by U.S.-based Fetullah Gulen, FETO is accused of orchestrating Turkey’s July 15 coup plot 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.

The July 15 defeated coup left 241 people martyred and some 2,200 injured.

Reporting by Ahmet Akbiyik :Writing by Hatice Kesgin