A UN investigation into the Israeli-Palestinian conflict in Gaza has found evidence that both sides committed "war crimes," the global body said Tuesday.

The investigation led by former South African judge Richard Goldstone concluded, according to the press release, that "Israel committed actions amounting to war crimes, possibly crimes against humanity," during its Dec. 27-Jan. 18 military operations in the Gaza Strip.

The report "concludes there is also evidence that Palestinian armed groups committed war crimes, as well as possibly crimes against humanity," by firing rockets at cities in southern Israel, the UN said.

Israel, which has refused to co-operate with the investigation, rejected the report's conclusion.

"The mandate of the mission and the resolution establishing it prejudged the outcome of any investigation, gave legitimacy to the Hamas terrorist organization and disregarded the deliberate Hamas strategy of using Palestinian civilians as cover for launching terrorist attacks," Israel's Foreign Ministry said in a statement distributed by the country's mission to the UN in Geneva.

The Palestinian group Hamas rules Gaza and has been accused by Israel of using human shields during the conflict, in which almost 1,400 Palestinians were killed — many of them civilians.

"Notwithstanding its reservations, Israel will read the report carefully," the Foreign Ministry said, noting that the Israeli Defence Force has examined more than 100 allegations regarding the conduct of its forces during the Gaza operation, resulting in 23 criminal investigations.

The 575-page report, which was released ahead of its presentation to the UN Human Rights Council later this month, said Israel's attacks in the Samouni neighbourhood of Zeitoun, south of Gaza City, including the shelling of a house where soldiers had forced Palestinian civilians to assemble, amounted to war crimes.

It found that seven incidents where civilians were shot while leaving their homes trying to run for safety, waving white flags and sometimes even following Israeli instructions, as well as the targeting of a mosque at prayer time, killing 15 people, were also war crimes.

A "direct and intentional attack" on the Al Quds Hospital and an adjacent ambulance depot in Gaza City "may constitute war crimes," the report said.

Several Palestinians told the mission they were used as human shields by the Israeli forces, the report said, noting the case of Majdi Abd Rabbo, a 39-year-old intelligence officer of the Palestinian authority who was forced to walk ahead of the troops as they searched his and his neighbour's house. Rabbo was forced to undress down to his underwear in front of the soldiers and his sons had to strip naked, the report said.

On the Palestinian side the report found that armed groups firing rockets into southern Israel from Gaza failed to distinguish between military targets and the civilian population.

"Where there is no intended military target and the rockets and mortars are launched into civilian areas, they constitute a deliberate attack against the civilian population," the report found.

"These actions would constitute war crimes and may amount to crimes against humanity."

Palestinian officials could not immediately be reached for comment.