Police in Turkey arrested 21 suspected members of the Islamic State extremist group on July 10, state media reported.
The suspects, including three foreigners, were detained during coordinated raids across the country, including in Istanbul and on Turkey's southern border, the Anadolu news agency said.
The foreigners, whose nationalities were not immediately disclosed, were planning to cross into Syria, the agency said.
Authorities also seized hunting rifles, ammunition, and documents belonging to the IS group as well electronic equipment and military uniforms, it added.
The arrests came after a two-day visit this week by a senior U.S. delegation during which Turkey pledged more cooperation in the fight against the IS militants in Syria.
Under pressure from fellow NATO members, Turkey has stepped up efforts to prevent foreign fighters crossing into neighboring Syria to join the IS group.
Thousands of foreigners have been barred from entering because of security concerns.
