A humanitarian truce in Gaza lay in tatters Saturday amid a new deadly wave of violence, which left 91 Palestinians dead, and the apparent capture by Hamas of an Israeli soldier.
US President Barack Obama called for the soldier to be "unconditionally" released, but also said more must be done to protect Gaza civilians.
Israeli Justice Minister Tzipi Livni, a member of the eight-strong security cabinet, accused Hamas of being behind the disappearance of the missing soldier and said the group would pay a high price.
However early Saturday the Ezzedine al-Qassam Brigades, Hamas' armed wing, said it had no information on the whereabouts of the missing soldier, 23-year-old Hadar Goldin.
"The Ezzedine al-Qassam Brigades has no information on this soldier. We have lost contact with one of our combatant groups, which was fighting in the sector where the soldier went missing and it is possible that our fighters and this soldier were killed," the group said in a statement.
The intensive fighting on Friday, which ensued after a planned three-day ceasefire collapsed, left a total of 91 Palestinians dead and 350 wounded said Palestinian emergency services spokesman Acjraf al-QodraFifteen of those victims, including five children aged 3-12, came from the same family whose house was destroyed, he added.
More than 1,500 Palestinians, the vast majority of them civilians, have been killed in almost four weeks of conflict, Qodra said.
Shelling killed dozens of people in southern Gaza hours into the truce, which began at 8:00 am (0500 GMT) Friday and had been due to last 72 hours.
Hamas accused Israel of breaking the short-lived ceasefire, while the Jewish state said it was responding to militant rocket fire.
The chances of a durable truce seemed as remote as ever after the probable capture of Israeli Second Lieutenant Goldin.
The military also announced that two soldiers had been killed in the same incident near the southern city of Rafah.
"Our initial indications suggest a soldier has been abducted by terrorists in an incident where terrorists breached the ceasefire," according to army spokesman Lieutenant Colonel Peter Lerner.
He said a suicide bomber blew himself up, adding that first reports "indicate that a soldier was seized".
In 2006, militants from Gaza captured Israeli conscript Gilad Shalit and held him for five years before freeing him in exchange for more than 1,000 Palestinian prisoners.
Friday's short truce gave brief respite to people in the battered Strip from fighting that has now killed 1,600 on the Palestinian side, mostly civilians, and 63 Israeli soldiers and three civilians on the other.
Within hours, air raid sirens were heard on the Israeli side, and heavy shelling resumed in Rafah.
An Israeli army spokeswoman said 51 rockets and mortar rounds hit Israel Friday, with another nine rockets shot down by the Iron Dome missile defence system.
Obama said the United States "unequivocally condemned "barbaric" Hamas and the Palestinian factions that were responsible for killing two Israeli soldiers, and abducting a third almost minutes after a ceasefire had been announced".
"If they are serious about trying to trying to resolve this situation, that soldier needs to be unconditionally released, as soon as possible."
Obama added: "We have also been clear that innocent civilians in Gaza caught in the crossfire have to weigh on our conscience and we have to do more to protect them."
Earlier on Friday, the Israeli military warned people in Gaza to remain at home, saying in voice messages to mobile phones that it was "pursuing terrorist elements in Rafah".
US Secretary of State John Kerry had said that once the ceasefire was under way, Israeli and Palestinian representatives, including from Hamas, would begin talks in Cairo on a more durable truce.
The Palestinian militant group Islamic Jihad later said Egypt was postponing the talks after news of the Israeli soldier's capture, but Cairo said the invitation to talk was "still in place".
And Palestinian president Mahmud Abbas said a joint delegation, including Hamas and Islamic Jihad, would travel to Cairo Saturday for talks despite the renewed fighting.
'Inexcusable' world silence
Before the truce, Israeli tank fire and aerial bombardment killed 14 Palestinians in Gaza, and the army said five soldiers died in mortar fire near the shared border.
Only minutes before the truce began, Palestinians continued to fire rockets into southern Israel, with five brought down by missile defences, army radio said.
In a speech published after the ceasefire broke down, Saudi King Abdullah denounced "inexcusable" world silence over Israel's "war crimes" in Gaza.
"We see the blood of our brothers in Palestine being shed in collective massacres, that have spared nobody, and in war crimes against humanity... all taking place under the eyes and ears of the international community... that has stood indifferently watching events in the whole region," he said, demanding a series of humanitarian breaks to ease conditions for Gaza's civilians.
Prime Minister Benjamin Netanyahu's office accused Hamas and other Gaza militants of "flagrantly violating" the ceasefire.
Hamas spokesman Fawzi Barhum responded that "it is the (Israeli) occupation which violated the ceasefire. The Palestinian resistance acted based on... the right to self defence."