According to Haber7 newspaper, the operation is taking place in 34 Turkish provinces. A large number of foreign nationals are among the 913 people currently in custody.
Turkey's political climate has deteriorated after suicide bombing in the border town of Suruc on July 20 that left 32 people dead and over 100 wounded, and the killings of two police officers in the southern city of Ceylanpinar on July 22.
The suicide bomber who carried out the attack in Suruc was reportedly affiliated with ISIL. The PKK claimed responsibility for killing, in Ceylanpinar, two policemen accused of alliance with ISIL, as an act of revenge for Suruc, a city with a majority Kurdish population.
Turkey shares a southern border with war-torn Syria and Iraq, where ISIL militants have seized large areas of land over the past two years.