Turkish police have reportedly detained approximately 400 suspected members of Islamic State (Isis) in raids across the country on Sunday (5 February).
Those arrested include foreigners and alleged terrorists suspected of planning attacks, reported Turkish news agency Anadolu.
Raids have been carried out in the capital of Ankara, where 60 people were detained, in addition to 150 suspects detained in Sanliurfa in the south-east.
Dozens more have been detained in provinces ranging from Bursa in the west to Bingol in the east.
Police also detained 18 suspects in Kocaeli and Istanbul, 47 in Gaziantep and 46 others in Bursa province.
In the usually peaceful Aegean city of Izmir, nine people suspected of travelling to and from Syria and planning attacks in the city were detained, Anadolu said.
The crackdown comes months after a man allegedly linked to IS (Daesh) opened fire in a nightclub in Istanbul on New Year's Eve, killing 39 people.
A manhunt ensued and Abdulgadir Masharipov, an Uzbek national, was arrested by Turkish police on 16 January, who authorities say confessed to the massacre.
Turkey has been shaken by a wave of terror attacks in 2016 that have killed hundreds. All have been claimed by IS and the Kurdistan Freedom Falcons (Teyrenbazen Azadiya Kurdistan; TAK).
In addition to the latest arrests, Turkey says at least 780 people, including 350 foreigners, remain in detention – some of whom have been convicted – over suspected links to the Islamist group, reported Reuters.
Turkey has also been engaged in a battle with IS in neighbouring Syria since August, however its President Bashar al-Assad has repeatedly condemned this action as a breach of international sovereignty.