Jerusalem (AFP) - Hundreds of ultra-Orthodox Jews demonstrated on Thursday in Israel against compulsory military service with more than 30 arrested, AFP photographers and police said.

For several days the ultra-Orthodox, who represent about 10 percent of the Israeli population and live in compliance with a strict interpretation of Jewish laws, have been protesting in locations across the country.

The demonstrations were apparently triggered by the arrest of an ultra-Orthodox youth who refused to attend an army recruitment post to enrol in military service.

"Police units arrested 31 suspects involved in disturbances in Jerusalem and Bet Shemesh," police spokesman Micky Rosenfeld said in a statement, referring to two major protests.

The demonstrators formed a human chain and chanted "Nazis" at the policemen, with police using a hose to scatter them, the AFP photographers said.

Military service, two years and eight months for men and two years for women, is compulsory for most Israelis, with the exception of Israeli Arabs.

The ultra-Orthodox are exempt if studying in yeshivas (religious schools), though the issue is controversial with secular Israelis and attempts have been made to remove the exemption.

Either way they must register at the recruitment office but some, inspired by rabbis hostile to any cooperation with the Israeli authorities, refuse to and are considered deserters.

The conscription of the ultra-Orthodox is regularly the source of clashes with the police.

Some of the ultra-Orthodox view military service as a source of temptation for young people who then leave the closed world of prayer and religious study.

Ultra-Orthodox women are exempt if they request and can perform civilian service.