State-run Turkish media said the arrests were made in at least nine cities and that police were also searching the offices of at least three trade unions in the capital, Ankara.
The detentions are said to be related to an ongoing investigation into the Kurdish Communities Union (KCK), a group accused of links to the outlawed Kurdistan Workers' Party (PKK).
The PKK has been fighting for autonomy in the country's largely Kurdish southeast for decades.
Hundreds of people, including elected Kurdish mayors and human rights activists, have been arrested as part of the probe that first began in 2009.
Compiled from agency reports