By Nidal al-Mughrabi

GAZA (Reuters) - Hamas leaders said on Saturday they had given their consent for the Palestinians to join the International Criminal Court (ICC), a move that could open up both Israel and the militant group to war crime probes over the fighting in Gaza.

Moussa Abu Marzouk, a Hamas leader based in Cairo, said he had signed a document Palestinian President Mahmoud Abbas says all factions must endorse before he proceeds with the ICC push.

If the Palestinians were to sign the ICC's founding treaty, the Rome Statute, the court would have jurisdiction over crimes committed in the Palestinian territories.

An investigation could then examine events as far back as mid-2002, when the ICC opened with a mandate to try individuals for war crimes, crimes against humanity and genocide.

Explaining the Islamist group's decision to sign, Hamas official Mushir al-Masri told Reuters: "There is nothing to fear, the Palestinian factions are leading legitimate resistance in keeping with all international laws and standards."

"We are in a state of self-defence," he added.

At a news conference in Cairo earlier on Saturday, Abbas said he had asked all factions to join the ICC bid, adding: "There will be results for them joining."

There was no immediate comment from Israel, which is also not an ICC member. It says Hamas has committed war crimes by both firing thousands of rockets indiscriminately at Israeli towns and cities and by using Gazans as human shields.

A statement from the office of Prime Minister Benjamin Netanyahu did not directly address the Hamas move, but it quoted the Israeli leader as telling U.N. Secretary General Ban Ki-moon Hamas was guilty of such crimes.

"Hamas hides behind the people of Gaza and fires at Israel with the aim of carrying out massacres of its civilians. That is a double war crime ... while Israel does not deliberately harm civilians," the statement quoted Netanyahu as saying in the telephone call on Saturday.

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Both Israel and Hamas defend their military operations as consistent with international law.

In a meeting with ICC prosecutors this month to push for an investigation, Palestinian Foreign Minister Riad al-Malki said there was "clear evidence" of war crimes by Israel during its offensive in Gaza launched on July 8.

Hamas, which dominates Gaza, is shunned by Israel and the West as a terrorist group. The Islamist group's founding charter calls for the destruction of the Jewish state.

HEAVY DEATH TOLL

Palestinian health officials say 2,078 people, most of them civilians, have been killed by Israel since it launched its offensive, which is intended to end the militants' rocket fire.

The United Nations Children Fund (UNICEF) said on Saturday at least 480 Palestinian children had been reported killed.

Israel says it does its utmost to avoid civilian casualties in Gaza. On the Israeli side, 64 soldiers and four civilians have been killed in the fighting.

There is little sign of the Gaza conflict ending. On Saturday, Israeli aircraft bombed the enclave and Palestinian militants fired rockets at the Jewish state, the military said. Gaza health officials said five people were killed in an Israeli strike on a house in central Gaza.

Malki says the Palestinian Authority's current U.N. status, upgraded to "non-member state" from "entity" by a vote of the General Assembly in 2012, qualified it to become an ICC member and a decision on whether to apply could happen very soon.

As neither Israel nor the Palestinians are ICC members, the court currently lacks jurisdiction over Gaza. This could be granted by a U.N. Security Council resolution, but Israel's main ally, the United States, would probably veto any such proposal.

Membership of the ICC opens countries to investigations both on their behalf and against them. Several powers, including the United States, have declined to ratify the ICC founding treaty, citing the possibility of politically motivated prosecutions.

The ICC is a court of last resort, meaning that it will only intervene when a country is found to be unwilling or unable to carry out its own investigation.

(Writing by Maayan Lubell; Editing by Gareth Jones and Stephen Powell)