The Commission of Inquiry on the 2014 Gaza conflict said in Geneva on Monday that it had received "credible allegations" the two sides had committed war crimes during the conflict, which killed more than 2,140 Palestinians, most of them civilians, and 73 people on the Israeli side, mostly soldiers.
"The extent of the devastation and human suffering in Gaza was unprecedented and will impact generations to come," said the chair of the commission, New York judge Mary McGowan Davis.
Israel, which has been harshly critical of the commission since its inception last year, blasted the report as biased, with Prime Minister Benjamin Netanyahu insisting his country "does not commit war crimes".
"Israel defends itself against a terror organization which calls for its destruction and that itself carries out war crimes," Netanyahu said in a statement, referring to Islamist movement Hamas that rules the Gaza Strip.
Hamas meanwhile hailed the report's "condemnation of the Zionist occupier for its war crimes".
The report criticized both sides, but especially decried the "huge firepower" Israel had used in Gaza, with more than 6,000 airstrikes and 50,000 artillery shells fired during the 51-day operation.
Israeli bombings kill 551 children
The bombings of residential buildings had especially dire consequences, wiping out entire families, with 551 children killed, a choked-up McGowan Davis told reporters in Geneva.
Hundreds of Palestinian civilians were killed in their own homes, and the report provided heart-wrenching testimony from a man who lost 19 of his relatives in an attack in Khan Younis on July 26th, including his mother and all of his children.
"We all died that day, even those who survived," he said.
According to the report, which will be presented to the UN Human Rights Council on June 29th, 742 people were killed in attacks on residential buildings, with at least 142 families losing three or more members.
"The fact that Israel did not revise its practice of air strikes, even after their dire effects on civilians became apparent, raises questions of whether this was part of a broader policy which was at least tacitly approved
at the highest level of government," the commission said in a statement.
But the investigators also condemned the "indiscriminate" firing of thousands of rockets and mortars at Israel, which it said appeared to have been intended to "spread terror" among Israeli civilians.
Palestinian armed groups fired 4,881 rockets and 1,753 mortars towards Israel, killing six civilians and injuring at least 1,600 others, it pointed out.
McGowan Davis said one Israeli woman had described the helplessness she felt when her grandchild pleaded with her to "stop the rockets".
The two-member commission also pointed out that tunnels dug by Palestinian militants into Israel had traumatized Israeli civilians "who feared they could be attacked at any moment by gunmen bursting out of the ground".
'Failure to achieve justice'
While the conflict has ended, McGowan Davis pointed to a "pervasive failure on all sides to achieve justice" for the wrongs committed, and the report urged Israel to "break with its recent lamentable track record in holding
The investigators were not granted entry to Israel or the conflict area, and relied instead on more than 280 confidential interviews and some 500 written submissions for their findings.
The report, initially scheduled for publication in March, was delayed after the head of the team was accused of pro-Palestinian bias and quit under Israeli pressure.
Israel was not satisfied and called for the entire inquiry to be shelved, insisting the commission and the Human Rights Council which created it are inherently biased against the Jewish state.
In the occupied West Bank, a senior official from the Palestine Liberation Organization said the report reinforces "our will to go to the International Criminal Court".
Palestinians have been seeking to open criminal proceedings against Israel at the ICC as part of an increased focus on diplomatic manoeuvring and appeals to international bodies.
The ICC prosecutor's office said Monday it was "taking cognizance of the (UN) report and will review it in the context of its ongoing preliminary examination," aimed at determining whether an investigation is warranted.
The UN investigators refused to say whether they thought the ICC was an appropriate forum for seeking accountability for the abuses committed during the 2014 Gaza conflict.
A resolution based on their report will likely be tabled at the Human Rights Council next week, but it remains unclear whether diplomats will be able to agree on what follow-up action is merited.
McGowan Davis said she hoped the report could help "push the ball of justice a little further down the field."