Thousands of people marched through Paris on Saturday to decry the proposed extension of a state of emergency imposed after the November Paris attacks.
Braving driving rain and shouting slogans including "state of emergency -- police state" the marchers protested loudly against a measure they see as curbing human rights.
Police put participation at 5,000 while organisers said some 20,000 people took part.
Several other cities including Toulouse in the south held smaller-scale marches organised by unions, human rights organisations and other pressure groups.
A further gripe is a government plan to strip convicted French-born terrorists of their citizenship if they have a second nationality.
That proposal has already triggered the resignation of Justice Minister Christiane Taubira who stood down in protest over the plan this week after the reforms were presented to parliament.
Parliament is due in the coming days to debate the state of emergency as President Francois Hollande seeks parliamentary approval to extend the current three-month measure, which expires on February 26.
The Senate is to vote on the proposal on February 9, followed by a vote in the National Assembly on February 16.
Concern has been growing about the state of emergency, introduced after coordinated gun and bomb attacks left 130 dead in Paris on November 13.
France's highest administrative court on Wednesday refused to lift the state of emergency.
The Council of State ruled that the "imminent danger justifying the state of emergency has not disappeared, given the ongoing terrorist threat and the risk of attacks."
But UN human rights experts last week said the measures placed what they saw as "excessive and disproportionate" restrictions on key rights.
Saturday's protesters demanded an end to the state of emergency and the nationality proposal, measures they say "strike at our freedom in the name of hypothetical security."
Marchers said they fear an open-ended state of emergency.
"Until when? The end of Daesh (Islamic State (ISIS) group)? Ten years? Never?" asked one woman, who gave her name as Chris, while another, Camille, said she feared that France is "experiencing a permanent coup d'etat."
Despite the popular concern, a recent poll showed 70 percent of French people back maintaining the state of emergency.