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Palestinians walk past the ruins of houses destroyed during the 50-day war in 2014Suhaib Salem/Reuters

A UN report on the 2014 Gaza war has accused Israel and Hamas of serious violations of humanitarian and international law, which may amount to war crimes.

The investigation of the UN Human Rights Council into the six-week conflict between Israel and the Palestinian militant group, which rules the occupied Gaza Strip, condemns the "unprecedented number of casualties" that left 2,251 Palestinians, including 1,462 civilians – 299 women and 551 children – dead.

Sixty-six Israeli soldiers and seven civilians in Israel were also killed in the fighting. At least 1,600 civilians were injured.

The UN report laments Israel failed to release enough information regarding the specific military objectives of its attack, noting that security concerns "do not relieve the authorities of their obligations under international law".

It goes on to say that considering the lack of information suggesting Israel's raids were done to prevent civilian casualties, "there are strong indications that these attacks could be disproportionate, and therefore amount to a war crime".

In six cases of air strikes on residential buildings, the commission said there was little or no information available to explain why they were considered legitimate military targets.

It called on the Israeli government to "explain the factual elements that rendered the houses or the persons present inside a military target".

"Should a strike directly and intentionally target a house in the absence of a specific military objective, this would amount to a violation of the principle of distinction," it read. "It may also constitute a direct attack against civilian objects or civilians, a war crime under international criminal law."

More than 1,500 children were orphaned in Gaza and the number of internally displaced persons reached 500,000 (28% of the population), while a total of 11,231 Palestinians were injured in the war.

"The effect of this devastation had a severe impact human rights of Palestinians in Gaza and will do so for generations to come," the report said.

It also criticised the use of rockets from Palestinian armed groups towards Israeli civilians whose main purpose was to "spread terror among the civilian population".

"The use of rockets in the possession of Palestinian armed groups, indiscriminate in nature, and any targeted mortar attack against civilians constitute violations of international humanitarian law, in particular of the fundamental principle of distinction, which may amount to a war crime," it says.

The independent investigators, led by American Mary McGowan Davis, also condemned executions of alleged "collaborators" by Palestinian groups saying they constituted war crimes.

The conclusions read:

"The commission is concerned that impunity prevails across the board for violations of international humanitarian law and international human rights law allegedly committed by Israeli forces," the report said.

"Israel must break with its recent lamentable track record in holding wrongdoers accountable, not only as a means to secure justice for victims but also to ensure the necessary guarantees for non-repetition.

"With regard to Palestinian armed groups, the commission has serious concerns with regard to the inherently indiscriminate nature of most of the projectiles directed towards Israel by these groups and to the targeting of civilians, which violate international humanitarian law and may amount to a war crime."