The United Arab Emirates pledged $25 million in humanitarian aid Thursday to "support the steadfastness" of Palestinians in Gaza where Israeli strikes have killed more than 70 people in three days.

The Emirati Red Crescent will supervise delivery of the aid, WAM state news agency said, adding that the aid organization will also set up a field hospital in Gaza "to help the victims of the Israeli aggression".

Egypt opened its Rafah border crossing to Gaza on Thursday to receive wounded Palestinians as Israel pounded the enclave with air strikes, an official at the border said.

Hospitals in north Sinai, which borders Gaza and Israel, have been placed on standby to receive the Palestinians, Egypt's official MENA news agency reported.

Three of the six Israelis held over the abduction and killing of a Palestinian teenager last week are to be released, Israeli media said on Wednesday.

"Three of six suspects in murder of Palestinian teen Mohammed Abu Khder to be freed Thursday," the Haaretz daily said.

Nobel peace laureate Desmond Tutu has lashed out at Israeli and Palestinian leaders for behaving "like children," seeking to blame each other for the latest bloody conflagration in the long-running conflict.

"Once again, the people of Israel and Palestine are embroiled in a deadly contest of tit-for-tat violence in which there can never be victors, only losers," the South African cleric said in a statement.

France strongly condemns “aggression” against Israel and stands with it in the face of rocket attacks from Gaza, the French president told the Israeli prime minister on Wednesday in a phone call.

Francois Hollande "expressed France's solidarity (with Israel) in the face of rocket fire from Gaza" and told Benjamin Netanyahu "that France strongly condemns these aggressions," said a statement from the French presidency.

Rockets capable of hitting deeper into Israel than ever before and naval commandos launching a beachhead assault show that Hamas has increased its capabilities with help from Iran and Syria, analysts said Wednesday.

The last Israeli offensive against Gaza was meant to have degraded the Palestinian militant group's capabilities but less than two years later, Hamas is firing new longer-range projectiles, they said.

Hamas rocket and mortar attacks on Israel may force the Jewish state, unable to quell the relentless fire with retaliatory air strikes, to invade the Gaza Strip and open up a long and deadly conflict.

- What are Hamas's objectives?

In Gaza's stifling midday heat, grieving relatives of a family killed in an Israeli air strike sit outside a mosque, weary from their Ramadan fast and nervously anticipating the next deadly blast.

The mourners, most of them men, have come to bury six members of the Hammad family, including a teenager and two women, killed when a missile slammed into their home in the northern Gaza town of Beit Hanun.

Egypt on Wednesday urged Israel and the Palestinian Islamist movement Hamas in Gaza to halt their escalating conflict but played down hopes of a Cairo-mediated truce.

Egypt, which has a 1979 peace treaty with Israel, played a key role in mediating ceasefires in past wars between Hamas and the Jewish state.

Israeli warplanes pounded Gaza Wednesday, killing at least 30 people in a major new confrontation with Palestinian militants, as Hamas flexed its firepower and sent thousands running for shelters across Israel.

As the death toll from Israel's two-day Operation Protective Edge reached 57, Palestinian President Mahmoud Abbas accused Israel of committing "genocide" in Gaza.