The demonstrations held Monday in all of Turkey's 81 provinces were organized as President Recep Tayyip Erdogan's government prepares this week to extend the state of emergency for a seventh time.
The opposition Republican People's Party, known as CHP, accuses the government of misusing its emergency powers to bypass parliament, erode democracy and to go after government critics.
The Turkish government insists the unusual powers it acquires during a state of emergency are needed to deal with ongoing security threats.
In Istanbul, hundreds of CHP supporters staged a protest on a street near Taksim Square after police blocked their access to the city's main square.