A three-day humanitarian truce in Gaza collapsed only hours after it began Friday amid a deadly new wave of violence and the apparent capture by Hamas of an Israeli soldier.
Intensive shelling killed dozens of people in southern Gaza hours into the short-lived truce, with Hamas accusing Israel of breaking the ceasefire and the Jewish state saying it was responding to rocket fire.
The skies over Gaza fell silent after the ceasefire announced overnight by US Secretary of State John Kerry, the longest one agreed upon of several since the conflict began on July 8.
Starting from 0500 GMT, it gave brief respite to people in the battered strip from fighting that has killed nearly 1,500 on the Palestinian side, mostly civilians, and 63 Israeli soldiers and three civilians on the other.
Within hours, air raid sirens warning of rocket fire were heard on the Israeli side of the border, and heavy shelling resumed in the southern Gaza city of Rafah, killing at least 35 people and wounding 100, medics said.
Shortly afterwards the Israeli army said the ceasefire was over and that it was searching for a soldier feared to have been captured in the enclave.
"Our initial indications suggest a soldier has been abducted by terrorists in an incident where terrorists breached the ceasefire," army spokesman Peter Lerner said.
Israeli forces were pressing their "activities on the ground", he said, before the military announced that two soldiers had been killed and named the missing man as Second Lieutenant Hadar Goldin, 23.
Israeli Prime Minister Benjamin Netanyahu's office accused Hamas and other Gaza militants of "flagrantly violating" the ceasefire.
- Mobile phone messages -
Hamas spokesman Fawzi Barhum countered, saying "it is the (Israeli) occupation which violated the ceasefire. The Palestinian resistance acted based on... the right to self defence."
AFP correspondents said there appeared to be fierce fighting in the vicinity of Rafah, and medics had trouble retrieving the dead and wounded.
The army warned people to remain in their homes, saying in voice messages to mobile phones that it was "pursuing terrorist elements in Rafah".
Kerry had said earlier that once the ceasefire was under way, Israeli and Palestinian representatives, including from Hamas, would begin talks in Cairo on a more durable truce.
Egypt had invited Israel and the Palestinian Authority to send delegates to Cairo for longer-term truce talks, with the foreign ministry emphasising the "importance of both sides committing to the ceasefire so the negotiations can take place in a favourable atmosphere".
But the Palestinian militant group Islamic Jihad later said Egypt was postponing the talks after news of the Israeli soldier's capture.
Even so, Palestinian president Mahmud Abbas said a joint Palestinian delegation, including Hamas and Islamic Jihad, will travel to Cairo Saturday for ceasefire talks despite the renewed fighting in Gaza.
- Brief calm -
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.
And only minutes before the truce took effect, Palestinians had continued to fire rockets into southern Israel, with five brought down by missile defences, army radio said.
While the ceasefire had been accepted in the name of all militant groups by Hamas, the main political and military power in Gaza, the Islamist movement stressed it was dependent on Israel reciprocating.
In a speech published after the ceasefire broke down, Saudi King Abdullah hit out at the "inexcusable" world silence over Israel's "war crimes" in Gaza.
"We see the blood of out 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," the king said.
"This silence is inexcusable" and will "result in a generation that rejects peace and believes only in violence," he said.
The truce had come after the UN Security Council expressed "grave disappointment" that repeated calls for one had not been heeded, and demanded a series of humanitarian breaks to ease conditions for Gaza's civilians.
It came after the White House said there was little doubt Israeli artillery was the source of a "totally indefensible" strike on a UN school in northern Gaza that killed 16 people on Wednesday.
The school was sheltering more than 3,000 Palestinians made homeless by the relentless fighting.
The Israeli army has suggested the deaths may have been the result of a misfired Palestinian rocket.