U.N. Secretary-General Ban Ki-moon urged an immediate end to the violence between the Israelis and Palestinians, which was headed into its sixth day. Ban said he would go to Cairo to try to help engineer a truce.
"This must stop," he said in a statement. "I strongly urge the parties to cooperate with all efforts led by Egypt to reach an immediate cease-fire."
Palestinian health officials said at least 26 Gazans were killed Sunday, including at least 14 women and children, the BBC reported.
The British network said more than 70 Palestinians and three Israelis have been killed since the latest outbreak of hostilities last week. Palestinian officials said at least 600 more have been wounded, The New York Times reported.
Israel's "Operation Pillar of Defense" has included more than 1,000 Israeli airstrikes in Gaza, while hundreds of Palestinian rockets have rained on Israel.
Israel said the bomb that wiped out 10 members of a family in its Gaza home and two neighbors was aimed at a top Hamas militant, the Israeli newspaper Haaretz reported. Israeli subsequently said the Hamas militant in question, Yehya Bayaa, may have survived the attack. Hama vowed to retaliate.
Haaretz quoted Israeli military officials as saying the wrong house was hit because of a "technical error."
Prime Minister Binyamin Netanyahu told reporters before his weekly Cabinet meeting Sunday Israel is prepared to escalate its military operation.
"We are exacting a heavy price from Hamas and the (other) terrorist organizations, and [Israel's military] is prepared for a significant expansion of its operations," Netanyahu said.
The BBC said Egyptian President Mohamed Morsi warned an Israeli ground invasion will have "serious repercussions" and added Egypt would never accept it "and neither will the free world."
U.N., Arab League and European diplomats -- including French Foreign Minister Laurent Fabius -- have been trying to defused the violence.
"War can be avoided," Fabius said after meeting Sunday with Netanyahu. "War must be avoided."
President Barack Obama said Sunday violence in Gaza threatened to further complicate the already slow progress toward a lasting peace in the region.
Speaking at a news conference in Thailand Sunday, the president said he had been in contact with the leaders of Egypt and Turkey and reminded them that a workable deal to end the current violence was vital.
"What I have said ... is that those who champion the cause of the Palestinians should recognize that if we see a further escalation of the situation in Gaza, then the likelihood of us getting back on any kind of peace track that leads to a two-state solution is going to be pushed off way into the future," he said.
Obama said halting Hamas rocket attacks was a required first step toward getting Israel to wind down its counteroffensive.
"There is no country on Earth that would tolerate missiles raining down on its citizens from outside its borders," he said. "So we are fully supportive of Israel's right to defend itself from missiles landing on people's homes and workplaces and potentially killing civilians."
Israeli officials said about 120 rockets were fired into Israel from Gaza Sunday -- with at least 38 of them intercepted by Israel's Iron Dome missile-defense system. However one rocket struck a vehicle in the town of Ofakim, injuring an undetermined number of people, and another struck a carport at a home with a woman inside the home, CNN said.
Explosions were heard around Gaza City, and Israeli forces said they knocked out a transmitter that Hamas had been using on the roof of a building used by international journalists.