Rolando Gomez, information officer for the Office of the High Commissioner for Human Rights, holds the report on the 2014 Gaza war on June 22 at the United Nations Office in Geneva. (Fabrice Coffrini/AFP/Getty Images)

A U.N.-backed commission presented findings Monday suggesting that both ­Israelis and Palestinians violated international law and committed possible war crimes during the Gaza war last summer that left thousands dead and wide swaths of the coastal enclave in ruins.

The long-awaited report laid blame at the feet of the Islamist militant movement Hamas and the Israeli military.

The conclusions presented by the panel — an independent body working for the U.N. Human Rights Council — could become part of the case file on the war at the International Criminal Court in The Hague, where a prosecutor is weighing whether to launch an official investigation.

Such an inquiry could place Hamas militia commanders and Israeli leaders beside notorious African warlords targeted by the international tribunal.

Israeli Prime Minister Benjamin Netanyahu called the report “flawed and biased” and urged the world to ignore it. Hamas praised the document and said it hoped Israeli leaders would soon find themselves prosecuted at the international court — even though the militant group could face charges as well.

Residence flee their homes after an Israeli air strike flattened a building across the street from theirs in their neighborhood of Tal al-Hawa Gaza in Gaza City on July 30, 2014. (Max Becherer/Polaris Images for The Washington Post)

“Impunity prevails across the board,” the panel members wrote. “Israel must break with its lamentable track record in holding wrong doers accountable, and accountability on the Palestinian side is also woefully inadequate.”

The panel added that it was “deeply moved by the immense suffering of Palestinian and ­Israeli victims, who have been subjected to repeated rounds of violence.”

The head of the commission, former New York Supreme Court justice Mary McGowan Davis, said at a news briefing in Geneva: “The extent of the devastation and human suffering in Gaza was unprecedented and will impact generations to come.”

She acknowledged, too, the “ongoing fear in Israel among communities who come under regular threat.”

The report said the summer conflict saw a huge increase in firepower over the previous two Gaza wars, “with more than 6,000 airstrikes by Israel and approximately 50,000 tank and artillery shells fired.”

From the Gaza side, the U.N. group said, Palestinian armed factions fired 4,881 rockets and 1,753 mortars toward Israel in July and August 2014.

“In some cases, these violations may amount to war crimes,” wrote the report’s panelists, who conducted the bulk of their research from Amman, Jordan, after Israel and Hamas refused to cooperate.

Israel has been bracing for the report for months. The Israeli military’s legal corps has issued summaries of its own investigations into alleged war crimes and concluded that while deadly mistakes occurred — such as an airstrike that left four Gaza boys dead on a beach — the Israeli actions were accidental and the military had sought to protect uninvolved civilians.

Even though Israelis knew the report was coming, many appeared particularly stung by its lumping together of the Israeli army with its arch enemy, Hamas. Israel and the United States consider Hamas a terrorist organization, and Israelis often call their armed forces “the most moral” in the world.

“Any fair inquiry into armed conflict must always draw a distinction between the aggressor and the side asserting its right to self-defense,” Dore Gold, director general of Israel’s Foreign Ministry, said in an interview. “The fact that the United Nations report fails to distinguish between Israel and Hamas is one of its most central flaws.”

Gold added: “It was Hamas that aimed rockets at Israeli civilian centers hoping to cause maximal casualties, and Israel whose strategy was to minimize civilian casualties. To compare the two is to ignore the glaring difference between how the sides approached the conflict.”

While the report cited Hamas and other armed Palestinian factions in Gaza for indiscriminate rocket fire targeting civilian areas inside Israel, the findings focused on Israel’s military conduct during its air and ground campaign.

The report criticized Israel for not sufficiently explaining its military objectives during the weeks of war and noted that Israel’s security considerations “do not relieve the authorities of their obligations under international law.”

“The onus remains on Israel to provide sufficient details on its targeting decisions to allow an independent assessment of the legality of the attacks conducted by the Israel Defense Forces,” the report said.

The report questioned Israel’s overall military policy, including the use of artillery, tank cannons and other less-precise weapons in densely populated areas and the destruction of entire neighborhoods in Gaza. It also asked why Israel failed to revise its rules of engagement and targeting decisions after seeing the death and destruction such fire caused.

The report acknowledged disparities in casualty counts by the United Nations, Israeli and Palestinian authorities, and human rights groups. But it pointed out that the “high incidence of loss of human life and injury . . . is heartbreaking.”

According to figures presented in the report, 2,251 Palestinians were killed during the hostilities, including 1,462 Palestinian civilians, of whom 299 were women and 551 children. Six Israeli civilians and 67 Israeli soldiers were killed.

Referring to the Palestinian armed groups, which the report criticizes for the “inherently indiscriminate nature of most of the projectiles directed towards Israel,” the commission suggested that such “violations of international humanitarian law . . . may amount to a war crime.”

The report also noted that the “increased level of fear among Israeli civilians resulting from the use of tunnels was palpable.” And it condemned the extrajudicial executions of alleged “collaborators,” a practice that the panelists said also “amounts to a war crime.”

The summer 2014 hostilities were triggered by a series of events including the kidnapping and murder of three Israeli teenagers in early June by Hamas operatives and the subsequent murder of a Palestinian teenager on July 2 by Jewish extremists. The events in the West Bank were accompanied by a surge of Palestinian rocket fire toward Israel, the report said.

Read more:

The U.N. report on Israel’s Gaza war: What you need to know

Israel says war in Gaza was moral and deaths are the fault of Hamas

Palestinians join international court to fight Israel

Today’s coverage from Post correspondents around the world