Thousands of ultra-Orthodox Jews have protested in Jerusalem against plans to enlist men from their community into the army.

Police spokesman Micky Rosenfeld said at least 20,000 protesters took part in Thursday's rally near the city's military draft bureau.

About a dozen arrests were made when violence erupted and men hurled bottles and stones at officers, some on horseback, who used stun grenades to quell the unrest.

A water cannon was also deployed as protesters set alight rubbish bins, a regular occurrence at ultra-Orthodox demonstrations. At least six officers required medical treatment and two were taken to hospital, Rosenfeld added.

Rabbis warned protesters that army service would irreparably harm their way of life.

"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.

An Israel Radio commentator said the participants came from the most hardline elements of the ultra-Orthodox community who shun any compromise with the authorities on army service, and even refuse to recognise Israel for religious reasons.

Religious grounds
Prime Minister Binyamin Netanyahu's coalition government has committed to increase drafting ultra-Orthodox men, most of whom receive exemptions on religious grounds, in order to share the national burden and reduce pressure on the middle classes.

The party of Finance Minister Yair Lapid, Netanyahu's main coalition partner, received wide support at the polls in January on a pledge to resist demands by religious parties and to spread the load of army service and taxation more evenly.

Military service is compulsory in Israel, with men serving three years and women two.

But tens of thousands of ultra-Orthodox are currently exempted from army service by virtue of being enrolled in religious seminaries, or yeshivas.

Any move to expand the draft is vehemently opposed by the two ultra-Orthodox parties, Shas and United Torah Judaism.

Ultra-Orthodox Jews make up some 10 percent of Israel's population of eight million. Most do not work and rely heavily on state subsidies for their religious studies and to support their families.

About 60 percent of ultra-Orthodox men engage in full-time Jewish religious studies, keeping them out of the labour market.

On Tuesday, the cabinet approved a budget draft that will slash spending and hike taxes this year, and next, to rein in a growing budget deficit.

Lapid has warned that failure to implement public spending cuts could cause an economic collapse.