Turkish police detained 20 suspected members of the Islamic State militant group in the southern city of Adana early on Thursday, the private Dogan news agency reported.
It said anti-terror police, supported by a helicopter, staged simultaneous raids on 22 addresses in the city after a tip-off that Islamic State cells were planning attacks.
The suspects, who included senior local figures in the group, were taken to Adana police headquarters for questioning, it said.
President Tayyip Erdogan has said Islamic State militants from the former Soviet Union were behind an attack on Istanbul’s main airport in June which killed 45 people. Dozens have been detained over the attack.
Islamic State controls an area of Syria along the Turkish border, east of Adana.
The city of Adana is near the Incirlik Air Base, where U.S. personnel are stationed and which is used for air missions in the fight against Islamic State.