Police began searches of the city's main Caglayan court and courts in the districts of Gaziosmanpasa and Bakirkoy with arrest warrants for 173 prosecutors and other judicial staff working there, the Dogan news agency said.
The accused are suspected of links to the US-based Islamic preacher Fethullah Gulen who Ankara blames for the June 15 failed putsch against President Recep Tayyip Erdogan.
It was not clear how many suspects had been detained in the raids.
According to official figures, more than 35,000 people have been detained so far in the post-coup crackdown against alleged Gulen supporters, although 11,597 of these have since been released.
In a separate development, the former chief prosecutor for the eastern region of Erzurum was detained late Sunday while trying to cross into Syria.
Ekrem Beyaztas was caught by border guards just south of the Turkish town of Kilis, a Turkish official said, asking not to be named. There was no indication over why he had been heading to Syria.
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