Israeli soldiers who served in the Gaza Strip during the offensive of December and January have spoken out about being ordered to shoot without hesitation, destroying houses and mosques with a general disregard for Palestinian lives.

In testimony that will fuel international and Arab demands for war crime investigations, 30 combat soldiers report that the army's priority was to minimise its own casualties to maintain Israeli public support for the three-week Operation Cast Lead.

One specific allegation is that Palestinians were used by the army as "human shields" despite a 2005 Israeli high court ruling outlawing the practice. "Not much was said about the issue of innocent civilians," a soldier said. "There was no need to use weapons like mortars or phosphorous," said another. "I have the feeling that the army was looking for the opportunity to show off its strength."

The 54 anonymous testimonies were collated by Breaking the Silence, a group that collects information on human rights abuses by the Israeli military. Many of the soldiers are still doing their compulsory national service.

Palestinians counted 1,400 dead but Israel put the death toll at 1,166 and estimated 295 fatalities were civilians. Ten soldiers and three Israeli civilians were killed.

Israel launched the attack after the expiry of a ceasefire designed to halt rocket fire from Gaza and crush the Islamist movement Hamas, which controls the coastal strip.

Witnesses described the destruction of hundreds of houses and many mosques without military reason, the firing of phosphorous shells into inhabited areas, the killing of innocents and the indiscriminate destruction of property.

Soldiers describe a "neighbour procedure" in which Palestinian civilians were forced to enter suspect buildings ahead of troops. They cite cases of civilians advancing in front of a soldier resting his rifle on the civilian's shoulder.

"We did not get instructions to shoot at anything that moved," said one soldier. "But we were generally instructed: if you feel threatened, shoot. They kept repeating to us that this is war and in war opening fire is not restricted."

Many testimonies are in line with claims by Amnesty International and other human rights organisations that Israeli actions were indiscriminate and disproportionate.

Another soldier testified: "You feel like a stupid little kid with a magnifying glass looking at ants, burning them. A 20-year-old kid should not have to do these kinds of things to other people."

The testimonies "expose significant gaps between the official army version of events and what really happened on the ground", Breaking the Silence said.

"This is an urgent call to Israeli society and its leaders to sober up and investigate anew the results of our actions."

Ehud Barak, Israel's defence minister, said: "Criticism directed at the IDF (Israel Defence Forces) by one organisation or another is inappropriate and is directed at the wrong place. The IDF is one of the most ethical armies in the world and acts in accordance with the highest moral code."

An IDF spokesman told the Ha'aretz newspaper: "The IDF regrets the fact that a human rights organisation would again present to the country and the world a report containing anonymous, generalised testimony without checking the details or their reliability, and without giving the IDF, as a matter of minimal fairness, the opportunity to check the matters and respond to them before publication."

An internal investigation by the Israeli military said troops fought lawfully although errors did take place, such as the deaths of 21 people in a house that had been wrongly targeted.