Anadolu Agency says the suspects were detained Thursday in the town of Osmangazi, in northwestern Bursa province.
The private DHA agency said police conducted simultaneous dawn raids at five separate locations to apprehend them.
Turkey was hit by a wave of attacks in 2015 and 2016 blamed on IS and Kurdish militants that killed around 300 people.
IS claimed responsibility for a gunman’s attack at an Istanbul nightclub during New Year celebrations in the early hours of 2017. The attack killed 39 people, most of them foreigners.