About 50 ultra-Orthodox Jews have been detained after demonstrations in several Israeli cities Tuesday turned violent, officials said early Wednesday.Demonstrators in several cities including Jerusalem were protesting the arrest of a young Orthodox conscientious objector. They clashed with police and lobbed stones, Israeli television reported.

Police "take zero tolerance toward violent riots" a statement said. It also said at least three officers were injured by stones thrown by the protesters and a police photograph showed one officer bleeding from the face.

Another policeman was taken to hospital with a dislocated shoulder from scuffles with the rioters.

Police said the biggest incident was in Jerusalem's ultra-Orthodox Mea Shearim neighbourhood, where hundreds of rioters blocked thoroughfares, stoned police and set refuse bins ablaze.

There were similar confrontations in the town of Beit Shemesh, west of Jerusalem; in ultra-Orthodox Bnei Brak, adjacent to Tel Aviv, and in the southern town of Ashdod, Rosenfeld said.

Many ultra-Orthodox oppose military service for their young men because they believe it exposes them to influences and temptations not found in the insular world of prayer and religious study.

They see the spiritual life as no less an act of service to the Jewish state than serving in the military.

Full-time seminary students can claim exemption or deferral from the draft but they must sign on at the enlistment office in order to qualify.

Some refuse to cooperate with any part of the process as a matter of principle and are then arrested as draft-dodgers.

Israeli men have to serve three years in the armed forces while women serve two years. Until recently ultra-Orthodox Jews were exempted from military service, and they have challenged reforms introduced in 2014 that call on them to serve.