JERUSALEM - Israeli police battled hundreds of ultra-Orthodox Jews protesting against conscription, arresting nearly 50 people overnight, a police spokesman said on Wednesday.
"There were 48 or 49 arrested across the country," Micky Rosenfeld said.
Police "take zero tolerance toward violent riots" a statement said.
Police 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.
The protests were apparently triggered by the earlier arrest of a young ultra-Orthodox man who refused to report to an army recruiting post to register for his compulsory three-year service.
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.
Military service is obligatory for Jewish Israelis after they turn 18 -- three years for men and two for women.
Ultra-Orthodox women do not serve.