Israeli air strikes killed 16 Palestinians in Gaza on Saturday, prompting the Arab League to announce a visit to the battered enclave and a review of its Middle East peace policy.
Egypt's President Mohamed Morsi told reporters in Cairo his government was in "vigorous" communication with both Israel and the Palestinians.
"There are some indications that there could be a ceasefire soon," Morsi told a joint news conference with Turkish Prime Minister Recep Tayyip Erdogan. But there were still "no guarantees", he added.
Hamas chief Khaled Meshaal was also in Cairo for talks, a senior Hamas official said.
Medics said 46 Gazans had been killed and more than 450 injured since Israel launched its air campaign on Wednesday, with at least nine militants among the 16 people killed on Saturday alone according to the latest tally.
As the toll rose, sirens sounded in Tel Aviv for a third day, sending people running for cover a day after a rocket fired by militants in Gaza hit the sea near the city centre, AFP correspondents said.
Israeli officials said one rocket was intercepted by the Iron Dome anti-missile system while a second hit somewhere in the Tel Aviv metropolitan area. The attack was claimed by Hamas's armed wing.
Warplanes carried out 180 air strikes on Gaza overnight, Israeli television reported, with attacks levelling the headquarters of the Hamas government.
Erdogan said Israel would be held to account for the children killed.
"Everyone must know that sooner or later there will be a holding to account for the massacre of these innocent children killed inhumanely in Gaza," he said in a speech in Cairo.
So far, six children have been killed, the Palestinian Centre for Human Rights said.
Turkey and Egypt have publicly shrugged off US bids to get them to exert pressure on the Islamist Hamas to get them to end their rocket fire. They have blamed Israel for the violence.
Arab foreign ministers at an emergency meeting in Cairo denounced Israel's Gaza campaign and demanded a review of their policy towards the Jewish state.
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A League statement said its chief Nabil al-Arabi will head a delegation to Gaza on Sunday or Monday "to affirm solidarity with the Palestinians."
It also said the ministers had decided to ask a League task force to review "the usefulness of continuing the Arab commitment in proposing the Arab peace initiative as a strategic choice."
In 2002, Arab states offered Israel diplomatic recognition in return for its withdrawal from all occupied territory and an equitable settlement of the Palestinian refugee question. That has been a cornerstone of Arab diplomacy ever since.
The statement urged Arab states to abide by previous League decisions to stop normalising ties with Israel. However, an Arab League diplomat said this would not affect the peace treaties Egypt and Jordan had signed with Israel.
US Deputy National Security Adviser Ben Rhodes said Saturday that President Barack Obama and Israeli Prime Minister Benjamin Netanyahu had agreed de-escalation in Gaza was preferable -- provided Hamas ceased fire.
"We believe that the precipitating factor for the conflict was the rocket fire coming out of Gaza," Rhodes told reporters aboard Air Force One.
"We believe that Israel has a right to defend itself, and they'll make their own decisions about the tactics that they use in that regard."
Amid diplomatic efforts to end the violence, French Foreign Minister Laurent Fabius was due in Jerusalem, Tel Aviv and the Palestinian territories on Sunday, Paris's embassy in Jerusalem announced. Palestinian officials said Fabius would meet president Mahmud Abbas in the West Bank city of Ramallah.
Since the start of Operation Pillar of Defence, the Israeli army says militants have fired more than 600 rockets over the border, of which 430 hit and 245 were intercepted by Iron Dome missiles.
Over the same period, three Israelis have been killed and 18 injured, including 10 soldiers. The army said the air force had hit more than 950 targets in Gaza.
Multiple Israeli air strikes on Gaza on Saturday killed 16 people, including at least nine militants.
Four Israeli soldiers and five civilians were hurt in separate rocket attacks on Saturday, police and the army said. Hamas claimed the attack on the soldiers, while Islamic Jihad said it fired rockets that injured civilians in Ashdod.
Late Friday, the military sealed off all main roads around Gaza, the latest sign it was poised to launch its first ground offensive on the territory since its 22-day campaign over New Year 2009.
Israeli ministers approved the call-up of as many as 75,000 reservists on Friday.