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.

Jordan, one of just two Arab countries to have signed a peace treaty with Israel, demanded Wednesday an immediate halt to deadly Israeli air raids against the Gaza Strip.

Government spokesman Mohammad Momani said that the raids that killed more than 20 Palestinians in purported response to rocket fire that has killed no one in Israel were "barbaric".

The European Union condemned "indiscriminate" rocket fire from the Gaza Strip into Israel on Tuesday and called for an immediate ceasefire as the Jewish state and Hamas squared off in their most serious conflict since 2012.

"The EU strongly condemns the indiscriminate fire into Israel by militant groups in the Gaza Strip," said a statement from the office of the bloc's foreign policy chief Catherine Ashton.

Turkey called on Israel on Tuesday to "immediately" halt its assault against the Gaza Strip, following the deadly air campaign against the Palestinian enclave.

"We are calling on Israel to immediately halt its attacks on Gaza," the foreign ministry said in a statement.

Israeli air strikes killed seven militants in Gaza overnight as clashes over the kidnap and murder of a Palestinian teenager raged into the early hours of Monday.

It was the worst bloodshed in Gaza since the start of the current round of violence in and around the territory, which began on June 12 in response to a vast West Bank arrest campaign to find those behind the kidnap and murder of three Israeli teenagers.

Egypt was on Friday mediating a potential ceasefire between Israel and Hamas, which controls the Gaza Strip, after a flare-up of violence across the border.

"There are continuing Egyptian efforts to return calm to the Gaza Strip, but no agreement has been reached yet," a Hamas official told AFP, on condition of anonymity.

Israel warned Hamas Thursday against any escalation in violence, reinforcing its Gaza border amid continued rocket fire and heightened tensions after three Israeli youths and a Palestinian teenager were murdered.

"We are looking for calm, not escalation, but if Hamas chooses to act against us, we shall be ready," armed forces chief Lieutenant General Benny Gantz said in remarks tweeted by the army.

Israel issued a brusque warning to Hamas on Monday, demanding it prevent rocket fire from Gaza as fears grew of a new confrontation around the coastal Palestinian enclave.

The military said an estimated 14 rockets slammed into Israel early in the morning, although the last struck at around 8.20 am (0520 GMT). Nobody was hurt.