51 ISIL suspects detained in Istanbul
Anti-terror squads conducted simultaneous raids in 11 districts to apprehend the suspects, who were allegedly plotting terror attacks, said the source, who spoke on condition of anonymity due to restrictions on speaking to the media.
Police also seized organizational documents and digital tools linked to the group.
Security forces have been involved in a long-running campaign to clear ISIL militants from Turkey.
More than 300 people lost their lives in ISIL-claimed attacks in Turkey, where the group has targeted civilians in suicide bomb, rocket, and gun attacks.