Thousands of ultra-Orthodox Jews have protested in Jerusalem against plans to force members of their community to serve in the Israeli military.
Several people were arrested after bottles, stones and a smoke grenade were thrown at police. Protesters and police were hurt in the clashes.
Ultra-Orthodox Israelis are currently exempt from military service while they study in religious schools or yeshivas.
Secular Israelis object to this and plans are being made to enlist them.
Military service is compulsory for most Israelis over the age of 18, with men serving three years and women two. But many Ultra-Orthodox Israeli men spend much of their adult life in religious studies.
At least 15,000 men, all dressed in the black coats and hats traditionally worn by Haredi (ultra-Orthodox) Jews, crowded into the streets around the military's recruitment office, in the Haredi neighbourhood of Mekor Barukh on Thursday night. Some estimates put the number of protesters much higher.
They were called to protest by two ultra-Orthodox factions which strictly oppose any change to the conscription laws which would make national service compulsory for their students.
"The government wants to uproot [our traditions] and secularise us, they call it a melting pot, but people cannot be melted. You cannot change our [way of life]," Rabbi David Zycherman told the crowd.
Protesters said prayers and chanted "the Torah [Jewish Bible] above everything!" and "the army will not take yeshiva pupils", AFP news agency reported.
Violence erupted as some threw missiles at police and set rubbish bins on fire. Pictures showed a policeman with blood streaming from a wound on his face, and a Haredi man with a bloodied nose.
The issue of exemptions for the ultra-Orthodox was a major part of January's elections in Israel. Centrist and secular parties which called for Haredi students to serve in the military received a lot of support and joined the government.
Ultra-Orthodox have been exempt from military service since the state was founded in 1948. They currently comprise about 10% of Israel's population, and in 2011 it was estimated about 37,000 ultra-Orthodox men were studying in yeshivas, and therefore not serving in the army. A small number of Haredi men already serve in the IDF (Israel Defence Forces).
Last year, Israel's Supreme Court ruled that the exemptions were unconstitutional and plans for a new law are under discussion.