The ongoing operation is targeting police officers accused of links to the network associated with Fethullah Gulen whom Ankara accuses of masterminding the July 15, 2016 attempted coup.
Turkish authorities have detained more than 1,000 people with suspected links to FETO, security sources said on Wednesday.
FETO (Fethullah Terrorist Organisation) is the acronym Ankara uses to refer to the network of US-based Fethullah Gulen, whom Turkey accuses of masterminding last year's attempted coup.
The overnight and early morning raids were the largest operations in months targeting the people Ankara blames for the attempted putsch on July 15, 2016 in which 249 people died and more than 2000 civilians were wounded.
Sources said the crackdown targeted the network's structure in the police force. Detention orders were issued for over 4,000 people. At least 1,009 were detained, the sources said, in operations carried out across all 81 of Turkey's provinces.
Ankara accuses Gulen and his group of a long-running campaign to overthrow the state through infiltrating government institutions, particularly the military, police and judiciary, and forming a "parallel state" structure.