Turkey has detained 21 suspected members of the Islamic State (IS) group, including three foreigners, in a major operation in several cities including Istanbul.
Police detained the suspects in pre-dawn raids in several addresses in Istanbul, as well as Sanliurfa province near the Syrian border, southern Mersin province and Kocaeli province east of Istanbul.
The detainees are suspected of helping the jihadist group recruit people from Europe, the official Anatolia news agency said.
The foreigners, whose nationalities were not immediately clear, were planning to cross into Syria, it added.
The operation appeared to be the largest one yet targeting IS suspects in Turkey, with arrests in the megacity Istanbul for the first time.
Arrest warrants were issued for at least 30 suspects, Anatolia said, adding that police also seized two hunting rifles, scores of bullets, documents belonging to IS as well electronic equipment and military uniforms.
Western states have repeatedly accused Turkey of not doing enough to halt the flow of jihadists across its 911-kilometre border with Syria.
Turkey fiercely rejects the accusations, saying it is making every effort to secure a long border and in turn has accused the West of not playing its part to shoulder the burden of hosting 1.8 million refugees from Syria.
In an apparent bid to deflect the criticism, Turkish authorities have arrested a number of suspected militants in recent months.
The arrests came after a two-day visit this week by a senior US delegation during which Turkey pledged more cooperation in the fight against the IS jihadists in Syria.
Turkey has reinforced its military presence on the volatile border over the past week, deploying tanks and anti-aircraft missiles there as well as additional troops.
The Turkish build-up has led to speculation that the government is planning to intervene in Syria to push the jihadists back from the border and halt the advance of Kurdish forces who have made gains against the extremists in the area.
Prime Minister Ahmet Davutoglu on Friday ruled out any prospect of an immediate intervention in Syria, but said Turkey would respond if its security was threatened.