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 …