Israelis protesting against contentious judicial reforms are blocking roads and railways in a "day of disruption".
In Tel Aviv, police used stun grenades and water cannon, and were filmed kneeling on the neck of a demonstrator as he was detained.
The protesters believe the sweeping changes being pushed through parliament will undermine judicial independence and threaten democracy.
Ministers say they will restore balance between the branches of government.
They have described the protesters as "anarchists".
Live footage from Tel Aviv showed a number of scuffles as police dragged away demonstrators. Officers on horseback tried to stop some breaking through barricades.
Speaking on Israeli Channel 13 TV, one protester called Zeev commented: "This is terrible violence, no-one touched the policemen. We were in a protest of civil people. We didn't expect such a thing. We are here to support democracy."
However, the far-right National Security Minister, Itamar Ben-Gvir, said police had been "very patient" and had barriers and stones thrown at them.
He backed the measures being used, saying the force "must use all the means at its disposal to maintain public order and the daily routine of Israeli citizens".
Prime Minister Benjamin Netanyahu wrote on Twitter: "The right to protest is not the right to anarchy."