A police statement said that "around 50" protesters cut off the north-south highway 4 in the predominantly ultra-Orthodox city of Bnei Brak.

An AFP journalist saw border police officers physically dragging away sit-down demonstrators.

Video footage aired on Israeli television channels showed appeared to be thousands more gathered nearby, chanting in support, with a police water cannon standing by.

They reported that the main highway was cleared after two hours.

There has been a string of demonstrations in recent months, spurred by arrests of young ultra-Orthodox men accused of dodging military service.

The issue triggered a potentially terminal crisis in Prime Minister Benjamin Netanyahu's ruling coalition, with ultra-Orthodox political parties threatening to break up the government unless a bill to exempt their youngsters from the draft was passed.

Defence Minister Avigdor Lieberman and his fiercely secular Yisrael Beitenu party want to see the ultra-Orthodox serve in the military like other Israelis and have vowed to fight the bill in parliament.

Israeli law requires men to serve two years and eight months in the military on reaching the age of 18, while women must serve for two.

There was a lull in the political infighting on Monday after a government committee approved sending the bill for a preliminary parliamentary reading, with a final vote not expected for months.

Lieberman told Yisrael Beitenu MPs that he would continue to oppose it but would remain in the government for now, although he could resign later.

Ultra-Orthodox men are excused from military service if they are engaged in religious study, but must still report to the army to receive their exemption.

Some seminary students have refused even to do that.

There were protests in Jerusalem last week, after the arrest of a young ultra-Orthodox man who failed to show up to request an exemption after receiving a call-up notice.