Israel-Gaza conflict
A file photo of smoke and explosion after Israeli air strikes in Gaza City in August 2014.Reuters

U.N. investigators said on Monday that Israel and Palestinian militant groups committed grave abuses of international humanitarian law during the 2014 Gaza conflict that may amount to war crimes.

In a report after a year-long inquiry, they called on Israel to explain its "targeting decisions" to allow independent assessment of its attacks on the Gaza Strip, where they said 1,462 civilians were killed and thousands of homes destroyed.

The independent investigators, led by American Mary McGowan Davis, also condemned what they found were executions of alleged Palestinian "collaborators" with Israel by militants in Gaza, saying these killings appeared to constitute war crimes.

A ceasefire last August ended 50 days of fighting between Gaza militants and Israel in which health officials said more than 2,100 Palestinians were killed. Israel put the number of its dead at 67 soldiers and six civilians.

Israeli air strikes and shelling hammered the densely-populated enclave dominated by the Islamist Hamas movement, causing widespread destruction of homes and schools. For their part, Gaza militants fired thousands of rockets and mortar bombs into Israel.

Both sides have denied violating the laws of war in the conflict.

"The commission was able to gather substantial information pointing to serious violations of international humanitarian law and international human rights law by Israel and by Palestinian armed groups. In some cases, these violations may amount to war crimes," the United Nations report said.

CALL ON ISRAEL TO EXPLAIN TARGETING DECISIONS

"The fact that the (Israeli) political and military leadership did not change its course of action, despite considerable information regarding the massive degree of death and destruction in Gaza, raises questions about potential violations of international humanitarian law by these officials, which may amount to war crimes."

The report said the onus was on Israel to provide details of how it chose its targets in Gaza to "allow an independent assessment of the legality of the attacks".

Palestinians joined the International Criminal Court (ICC) after the war, a move opposed by Israel, and the Hague-based court is examining possible war crimes in the conflict.

William Schabas, who initially headed the U.N. inquiry, quit in February over Israeli accusations of bias due to consultancy work he had done for the Palestine Liberation Organisation.

Schabas was not involved in writing the report although he took part in the research, U.N. officials and diplomats say.

Israel issued a report earlier this month arguing its 2014 Gaza offensive was lawful, a move aimed at pre-empting the release of findings of the U.N. investigation that Prime Minister Benjamin Netanyahu scorned as a waste of time.

Amnesty International said in late May that Hamas committed war crimes, including abductions, torture and unlawful killings, against Palestinian civilians it accused of "collaborating" with Israel during the conflict.

Hamas has denied any wrongdoing in the Gaza conflict, saying it acted to protect Palestinians.

The United States, the Israelis' staunch ally in the U.N. Human Rights Council, accuses the Geneva forum of a long-standing bias against Israel. It said the U.N. report had "problematic origins" as its authors lacked experience of international humanitarian law.