Some 450 suspects were picked up in the initial phase of the nationwide operation yesterday but the number held has now risen to 763, the Anadolu news agency said.
It said raids took place in 29 of Turkey's 81 provinces and documents, weapons and ammunition were also seized.
The operation came just over a month after 39 people, mainly foreigners, were killed on New Year's night when a gunman went on the rampage inside a plush Istanbul nightclub.
Turkish police have over the last few years launched numerous raids against IS suspects but a nationwide operation on this scale against the group is unprecedented.
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Anadolu quoted Turkey's police directorate as saying that IS was looking to stage a "sensational action" inside the country for propaganda purposes, with media organisations seen as a possible target.
No further details were given.
Turkey was long accused by its Western allies of not doing enough to stop the flow of jihadists across its borders and emergence of IS cells in its own cities.
Police captured alive the suspected Reina nightclub attacker, Abdulgadir Masharipov, an Uzbek national, on January 16 after more than two weeks on the run and observers believe he may provide crucial intelligence.
According to media reports, Masharipov had also considered attacking Istanbul's main Taksim Square as well as the offices of the opposition Cumhuriyet newspaper.