As the conflict entered its third week, neither side showed any sign of willingness to pull back, with Israel pursuing a relentless campaign of shelling and air strikes, and militants hitting back with rocket fire and fierce attacks on troops operating on the ground.
Gaza medics say the Palestinian dead include many women and children, while 27 of the 29 Israeli victims were soldiers killed since a ground assault began late on July 17.
On Tuesday morning, civil defence crews with a crane parked outside the Salam building in Gaza City, which was hit in an Israeli air strike on Monday.
The tower block's top five floors had collapsed onto its bottom four floors. The leg of a person was visible from the street, lying on a piece of rubble caked with streams of dried blood.
World powers have urged Hamas to accept an Egyptian-brokered ceasefire and stop raining rockets into Israel from the Gaza Strip, demands it has so far resisted.
Kerry opened talks with Egyptian Foreign Minister Sameh Shoukri and later met the president, former military chief Abdel Fattah al-Sisi.
- 'Very complicated issues' -
Washington's top diplomat, who has invested much of his tenure in an unsuccessful bid for a lasting Middle East peace agreement, said he would discuss the Egyptian proposal, which calls for a ceasefire followed by negotiations.
The talks were on "how we can build on it and hopefully find not only a way to a ceasefire but a way to deal with the underlying issues, which are very complicated," he said.
UN chief Ban Ki-moon, who has also come to the Egyptian capital to push for a truce, was to hold separate talks with Sisi on Tuesday before heading to Jerusalem to meet with Israeli Prime Minister Benjamin Netanyahu.
Kerry has demanded that Hamas agree to end the fighting to spare further bloodshed, in a call echoed by the Arab League.
"Only Hamas now needs to make the decision to spare innocent civilians from this violence," he said on Monday.
As the diplomatic push gathered steam, Hamas leader Khaled Meshaal and Palestinian president Mahmud Abbas held talks in Doha, pledging to work together for a ceasefire and to lift the blockade on Gaza.
"Hamas and Abbas agreed that all Palestinian factions should work as a team towards a ceasefire," Azzam al-Ahmed, a senior official in Abbas's Fatah party, told AFP after Monday's meeting.
"It was decided that there should be a ceasefire first, and we will continue discussions with Egypt and all regional and international sides until we crystallise the content of a final peace agreement."
A senior Hamas official, however, said the movement was insisting on a full agreement before it ceased firing.
There was no halt to the bloodshed in Gaza, with at least 20 people killed in fresh Israeli strikes on Tuesday, raising the death toll since Israel launched its operation on July 8 to 593, emergency services spokesman Ashraf al-Qudra said.
- 100,000 displaced -
Nine of Tuesday's dead were women, one of whom was pregnant, and the toll also included a four-year-old girl, and five members of the same family, who died in a strike on Deir al-Balah in central Gaza.
Another 3,640 people have been wounded.
Israel has said Operation Protective Edge is to stamp out rocket fire from Gaza, and on July 17 it sent in ground troops to destroy cross-border tunnels used by Hamas militants to infiltrate southern Israel.
Since the offensive, more than 100,000 Gazans have fled their homes, seeking shelter in 69 schools run by the Palestinian refugee agency UNRWA.
- Another 2 soldiers killed -
Early Tuesday, the Israeli army said another two of its troops had been killed in clashes in Gaza a day earlier, raising Monday's toll to nine soldiers.
It confirmed that a soldier Hamas claimed to have captured two days ago -- Oron Shaul -- was dead but that his body remains unaccounted for.
Overall, 27 soldiers have died in the past four days, with 13 killed on Sunday alone in what was the bloodiest single day for the Israeli military since the Lebanon war of 2006.
Two Israeli civilians have also been killed by rocket fire.