The Israeli army has been forced to open an investigation into the conduct of its troops in Gaza after damning testimony from its own front line soldiers revealed the killing of civilians and rules of engagement so lax that one combatant said that they amounted on occasion to “cold-blooded murder”.

The revelations, compiled by the head of an Israel military academy who declared that he was “shocked” at the findings, come as international rights groups are calling for independent inquiries into the conduct of both sides in the three-week Israeli offensive against Palestinian Islamists.

The soldiers’ testimonies include accounts of an unarmed old woman being shot at a distance of 100 yards, a woman and her two children being killed after Israeli soldiers ordered them from their house into the line of fire of a sniper and soldiers clearing houses by shooting anyone they encountered on sight.

“That’s the beauty of Gaza. You see a man walking, he doesn’t have to have a weapon, and you can shoot him,” one soldier told Danny Zamir, the head of the Rabin pre-military academy, who asked him why a company commander ordered an elderly woman to be shot.

"I gathered the graduate students of the course who fought in Gaza, to hear their impressions from the fighting. I wasn't prepared for any of the stuff I heard there. I was shocked,” Mr Zamir said. “I think that the writing was on the wall, but we just didn't want to see it, we didn't want to face it."

One non-commissioned officer told Mr Zamir, himself a deputy battalion commander in the reserves, that the army “fired a lot of rounds and killed a lot of people in order for us not to be injured or shot at.

"When we entered a house, we were supposed to bust down the door and start shooting inside and just go up storey by storey… I call that murder. Each storey, if we identify a person, we shoot them. I asked myself – how is this reasonable?"

The same unnamed NCO said that his commanding officer ordered soldiers on to a rooftop to shoot an old woman crossing a main street during the fighting, which a Palestinian rights groups said left 1,434 people dead, 960 of them civilians.

"I don't know whether she was suspicious, not suspicious, I don't know her story,” the NCO said. “I do know that my officer sent people to the roof in order to take her out… It was cold-blooded murder."

Another NCO recounted a military blunder that led to a mother and her two children being shot dead by an Israeli sniper. "We had taken over the house… and the family was released and told to go right. A mother and two children got confused and went left… The sniper on the roof wasn't told that this was okay and that he shouldn't shoot… you can say he just did what he was told… he was told not to let anyone approach the left flank and he shot at them.

"I don't know whether he first shot at their feet or not, but he killed them," the soldier said.

The soldiers’ accounts were submitted anonymously at a meeting at the academy around a month ago. The Israel army said that it had started an investigation, but that this was the first time it had heard such testimony, despite having debriefed troops itself.

Breaking The Silence, an organisation of former soldiers who gather witness accounts from troops in the Palestinian territories, said that its own investigation into Operation Cast Lead, as the war was known in Israel, had revealed a similar picture of the fighting.

“It’s definitely in line with what we are hearing,” said one of the researchers.

Another disturbing element reported by the soldiers was the role of military rabbis in distributing booklets that framed the fighting as a religious war. “All these articles had a clear message: we are the Jewish people, we have come to the land by miraculous means, and now we have to fight to remove the Gentiles who are getting in our way and preventing us from occupying the Holy Land… a great many soldiers had a feeling throughout this operation of a religious war,” said one soldier.

There were also accounts of soldiers being ordered to throw all the furniture out of Palestinians’ homes as they were taken over.

“We simply threw everything out the windows to make room and order. The entire contents of the house flew out the windows: refrigerator, plates, furniture. The order was to remove the entire contents of the house.”

The Palestinian Centre for Human Rights released the names of 1,417 Gazans that it says were killed in the war, saying that 926 were civilians. The Israeli Government contends that most of those killed were combatants or legitimate targets.

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