Thousands of ultra-Orthodox Jews protested in Jerusalem on Thursday against any plans to make them undergo military service, a police spokesman said.

"At least 15,000 haredim (ultra-Orthodox) gathered outside the army recruiting office in Jerusalem," the spokesman said.

He said the demonstrators threw stones and "other objects" at security personnel.

Protesters also prayed and chanted "the Torah above everything!" referring to Jewish religious law, and "the army will not take yeshiva (religious seminary) pupils."

Police deployed in force to prevent any trouble, and at least five demonstrators were arrested, an AFP journalist said.

"We will not allow breaches of the peace," police spokesman Micky Rosenfeld told AFP.

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 yeshivas.

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

Several proposals on expanding the draft are under discussion, but ultra-Orthodox rabbis say their pupils' religious studies come first.