Turkish police detained 82 suspected Islamic State members, 77 of them foreign nationals, in raids across Istanbul, state-run Anadolu news agency reported on Saturday.
It said counter-terror police squads targeted suspects believed to have acted on behalf of the jihadists, going to conflict zones in Syria and Iraq and preparing urban attacks in Turkey.
Simultaneous police raids were carried out on 16 addresses in 10 districts of Istanbul, the agency said, without specifying when the operation was conducted.
The Anadolu report did not specify what evidence police had against the suspects but said police seized digital materials and documents during the raids.
Turkey has been a partner in the US-led coalition against Islamic State fighters, detaining more than 5,000 Islamic State suspects and deporting several thousand foreign militants in recent years.
Turkish police previously stepped up operations against Islamic State suspects at the end of last year ahead of the first anniversary of a New Year gun attack on a nightclub in Istanbul in which 39 people were killed.
Islamic State claimed responsibility for that shooting, which was one of a series of attacks believed to have been carried out by the jihadists in Turkey in recent years.