Israel's military must not give in to Jewish religious demands to prevent the mixing of men and women in the ranks, a group of reservist generals told the country's defence minister on Monday.

The 19 generals, among them former army, air force and navy commanders, listed times when they said women had been sidelined or segregated during military events because of pressure from male Orthodox soldiers.

"These include ... the separation of women soldiers from their units during ceremonies as a result of religious considerations, demands to prevent women from singing at such events and the demand that women be fenced in a closed, isolated area when (holiday) dances were held," they said.

The letter called on Defence Minister Ehud Barak and Chief of Staff Lieutenant-General Benny Gantz "to issue immediate, detailed directives to (Israeli military) units to refrain from imposing religious norms on male and female soldiers".

The appeal, printed in the Haaretz newspaper, opened a new front in an emotional public battle over what the military has acknowledged is a growing influence of religion in its ranks.

It comes against a backdrop of a broader debate on the increasing prominence of religion in Israel.

"We believe that it is the (Israeli military's) obligation to protect the rights of all people who serve in its ranks, and that joint service by women and men ... is a cornerstone of its character as the people's army," the generals wrote.

On its website, the military says it is committed to being "a leading organisation in society where women and men work as one" and providing "equal opportunities based on ... talent and merit".

Military service is mandatory in Israel for Jewish men and women, who are conscripted at the age of 18. Men serve for three years, women for two, with the prospect of reserve duty after their discharge.

One out of three Israeli soldiers is a woman and they can be deployed in 90 percent of all positions within the military, official statistics show.

EXCLUSION

Ran Goren, one of the signatories of the letter and a former head of the army's human resources branch, said on Israel Radio that women were increasingly being excluded from combat units that have a high percentage of Orthodox soldiers.

"To avoid problems, male soldiers are preferred over female ones," he said.

Avichai Ronsky, a former chief rabbi of the Israeli armed forces, said he respected the reservist generals who signed the letter but added they had to recognise the balance of secular and religious forces in the military was changing.

"They don't know what life is like today. The reality is different. There are many religious commanders ... and some places require special arrangements," Ronsky told the radio.

The military says it does not monitor its soldiers' religious beliefs. But its "Maarchot" journal published a study last year that showed about a third of the graduates of an officer's training course considered themselves religious, compared with about 12 percent of the general population.

In a move that recently grabbed headlines in Israel, the military said it was assigning reservist army rabbis to battalions along the northern frontier to promote religious values. Critics said the military was becoming a "God's army".

While rabbis have long served in Israel's armed forces, their roles traditionally have focused on overseeing adherence to Jewish dietary laws in its kitchens, Sabbath observance and religious ceremonies.