While the air strikes relentlessly targeted militant rocket operations, Israeli gunboats unleashed a steady tattoo of heavy machine gun fire and shells at militant facilities on Gaza's coastal road.
The bloodshed was likely to raise pressure on Israel to end the fighting, even as it pledged to intensify the offensive by striking the homes of wanted militants. High numbers of civilian casualties in an offensive four years ago led to fierce criticism and condemnation of Israel.
In all, 81 Palestinians, about half of them civilians, have been killed in the five-day onslaught and 720 have been wounded. Three Israeli civilians have died from Palestinian rocket fire and dozens have been wounded.
President Barack Obama said he was in touch with players across the region in hopes of halting the fighting, while also warning of the risks of Israel expanding its air assault into a ground war.
"We're going to have to see what kind of progress we can make in the next 24, 36, 48 hours," Obama said during a visit in Thailand.
UN chief Ban Ki-moon urged the two warring parties to achieve an immediate cease-fire. He said he was heading to the region to appeal personally for an end to the violence, but no date was given in the UN statement for his arrival.
On the ground, there were no signs of any letup in the fighting as Israel announced it was widening the offensive to target the military commanders of the ruling Hamas group.
The Israeli military carried out dozens of air strikes throughout the day, and naval forces bombarded targets along Gaza's Mediterranean coast. Many of the attacks focused on homes where militant leaders or weapons were believed to be hidden.
Palestinian militants continued to barrage Israel with rockets, firing more than 100 yesterday, and setting off air raid sirens across the southern part of the country. Some 40 rockets were intercepted by Israel's US-financed 'Iron Dome' rocket-defence system, including two that targeted the metropolis of Tel Aviv. At least 10 Israelis were wounded by shrapnel.
Israel's decision to step up its attacks in Gaza marked a new and risky phase of the operation, given the likelihood of civilian casualties in the densely populated territory of 1.6m Palestinians. Israel launched the offensive last Wednesday in what it said was an effort to end months of intensifying rocket fire from the Hamas-ruled Gaza Strip.
In the day's deadliest violence, the Israeli navy fired at a home where it said a top wanted militant was hiding. The missile struck the home of the Daloo family in Gaza City, reducing the structure to rubble.
Frantic rescuers, bolstered by bulldozers, pulled the limp bodies of children from the ruins of the house, including a toddler and a five-year-old. The bodies of the children were laid out in the morgue of Gaza City's Shifa Hospital.