Turkey announced that a massive anti-ISIS police operation carried out early Sunday morning led to the arrest of more than 440 people with alleged links to the terrorist organization. The counterterrorism operation was carried out across 18 provinces, including Istanbul, the capital Ankara, and Gaziantep, a city near the Syrian border that is a popular point of departure for individuals crossing over into Syria, Turkey’s state-run Anadolu Agency reported. Most of the detained suspects were foreign nationals.

Over the past year and a half, Turkey has seen a sharp spike in ISIS-inspired and organized attacks in the country that have left hundreds dead. The most recent high-profile attacks carried out in the name of the terrorist organization were the attack on Istanbul’s Ataturk International Airport last summer and the New Year’s Eve attack on partygoers at an Istanbul nightclub. Both incidents left dozens dead.

The Turkish military has also stepped up its military effort in northern Syria and on Sunday announced it had hit more than 250 ISIS targets across the border, killing 33 terrorists.