A police statement said four officers were slightly injured in scuffles as law enforcement tried to disperse "several hundred ultra-Orthodox extremists" outside an army enlistment office in the holy city.

"Police used stun grenades and water cannon against rioters," police spokesman Micky Rosenfeld told AFP.

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 years.

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 have been protests since the beginning of March, after the arrest of a young ultra-Orthodox man who failed to show up to request an exemption after receiving a call-up notice.

Last month the issue sparked a crisis in Prime Minister Benjamin Netanyahu's factious coalition government, with ultra-Orthodox parties threatening to torpedo a crucial budget vote.

The crisis was revolved for with a compromise in which the ultra-Orthodox supported the budget, while Netanyahu promised to give coalition MPs freedom on how to vote on a future bill on draft exemptions.

Hardline ultra-Orthodox youngsters, however, continue to block roads and scuffle with police in Jerusalem and elsewhere, in protests against military service.