Turkish police raided a number of addresses in four provinces early Friday morning as part of operations against suspected Daesh militants.

According to the security forces, police detained 21 Daesh suspects – including three foreigners – during separate operations which were carried out in Istanbul, Kocaeli and the southern provinces of Mersin and Sanliurfa.

According to local media, Turkish police had a list of 30 Daesh suspects in Istanbul; one of the operations was carried out amid tight security in the city’s working-class Gaziosmanpasa district.

Two automatic rifles, a large number of ammunition, organizational documents and military uniforms were seized in the raids; the three foreign suspects were reportedly preparing to go to Syria.

Detainees were taken to police headquarters in the various provinces after health checks.

Hundreds of people from European countries have reportedly gone to Syria and Iraq to join Daesh, which declared a so-called ‘caliphate’ in June 2014.

A number of massacres perpetrated by Daesh last year – along with the forced deportation of minority populations from areas under its control – led to the establishment of a U.S.-led international coalition last September to combat the extremist group.