Turkish police say at least 51 suspected Daesh militants have been detained in simultaneous raids around Istanbul.

A statement from Istanbul's police headquarters said Friday that anti-terror units raided 16 different locations in the city, detaining suspects it described as "foreign fighters."

All of them were foreign nationals, the statement said, without providing details on their countries of origins.

The suspects had either traveled or were planning to travel to "conflict zones," the statement added in an apparent reference to Syria or Iraq.

In a separate operation, four Daesh suspects have been detained in Başiskele and Izmit districts of northwestern Kocaeli province.

Turkey has suffered a series of deadly attacks blamed on Daesh militants, including a New Year's attack at an Istanbul nightclub in the early hours of 2017 that killed 39 people and the country's deadliest terror attack on Oct. 10, 2015 at a peace rally in Ankara that killed 107 people.