The testimonies appeared in a 237-page report called "This is how we fought in Gaza" which was based on the anonymous accounts of 60 soldiers and officers involved in the 50-day war last summer.
They were collated by Breaking the Silence, an Israeli non-governmental organisation whose members bear witness to abuses they have seen or taken part in during their military service in the occupied Palestinian territories.
But the Israeli army questioned the veracity of the report, saying the group had failed to provide "proof" of the witness accounts.
The report gave more than 100 examples of apparent misconduct during the war.
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One soldier related how troops were instructed to "open fire everywhere, first thing as you go in... The assumption being that the moment we went in, anyone who dared poke his head out was a terrorist".
"The instructions were to shoot right away. Whoever you spot -- be they armed or unarmed, no matter what. The instructions are very clear. Any person you run into, that you see with your eyes -- shoot to kill," said another.
A separate testimony said that two women who were talking on phones just under a kilometre away from the front line were shot dead.
When the bodies were later discovered to be unarmed, "we moved on, and they were listed as terrorists", the soldier said.