Israel inflicted "massive and unprecedented harm" to Palestinian civilians in the 2014 Gaza war with indiscriminate fire and lax rules of engagement, a report said on Monday, citing testimony given anonymously by dozens of troops.
The 237-page report by the Israeli advocacy group Breaking the Silence described how Israel Defence Forces (IDF) left swathes of devastation after they invaded Gaza last July with the stated aim of halting Hamas rocket fire out of the enclave.
"We were firing purposelessly all day long. Hamas was nowhere to be seen," one tank sergeant was quoted as saying.
The group said its finding cast "grave doubt on the IDF's ethics". The Israeli military says it tried to prevent non-combatant casualties, and accuses Hamas of inviting these by fighting from within residential areas.
The Palestinian Islamist group has been criticised abroad for firing rockets at Israeli civilians.
Some 2,256 Palestinians were killed during the July-August conflict, of whom 1,563 were civilians, according to U.N. figures. On the Israeli side, 66 soldiers and five civilians died.
The lopsided tolls have fuelled foreign criticism of Israel and Palestinian calls for war-crimes suits.
Monday's report suggested the IDF looked to minimise the risk to their own troops even if that meant harming civilians.
An infantry sergeant is quoted as saying that, once Israel deemed civilians had mostly fled an area of operations, "there weren't really any rules of engagement".
"The idea was, if you spot something, shoot," he said. "If you shoot someone in Gaza it's cool, no big deal." Israel questioned the methodology and motivations behind the report.
"Unfortunately, as in the past, Breaking the Silence has refused to provide the IDF with any proof of their claims," a military spokesperson said.
"This pattern ... indicates that contrary to their claims this organization does not act with the intention of correcting any wrongdoings they allegedly uncovered."
Breaking the Silence, which listed the Swiss foreign ministry and the Norwegian embassy among its Western donors, said it collected testimony from more than 60 war veterans and called for an external probe "that can examine conduct at the highest ranks in the security and political establishments".
The IDF has launched several internal investigations into the war and says these should suffice.
Publication of the report coincided with a conference organised by the Shurat Hadin Israel Law Center advocacy group, which argues Western democracies pitted against militants like Hamas require a "new law of war". Keynote speaker Benny Gantz, Israel's armed forces chief during the Gaza war, defended his troops' conduct as legal and predicted bloodier conflict in the future given the difficulty in distinguishing between Palestinian fighters and civilians.
"Next time, it will be worse, because Israel has to constantly grapple with the moral dilemma, but we need to protect our country," Gantz said. Asked by Reuters about the Breaking the Silence report, the ex-general declined comment.