A 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 truce, which began at 8:00 am (0500 GMT) and was due to last 72 hours.
But the ceasefire was short-lived, with Hamas accusing Israel of breaking it and the Jewish state saying it was responding to rocket fire.
Media reports said Israel's security cabinet was to meet later Friday in the wake of the breakdown.
The chances of a durable truce seemed as remote as ever with the probable capture of Israeli Second Lieutenant Hadar Goldin, 23.
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," army spokesman Peter Lerner said.
He said a suicide bomber blew himself up, and added that first reports "indicate that a soldier was seized".
In 2006, Hamas captured Israeli conscript Gilad Shalit and held him for five years before freeing him in exchange for more than 1,000 Palestinian prisoners.
- Brief respite -
Earlier Friday, the skies over Gaza fell silent after the ceasefire was announced overnight by US Secretary of State John Kerry, in what would have been the longest of several agreed since the conflict began on July 8.
The short truce gave brief respite to people in the battered Strip from fighting that has killed at least 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, and heavy shelling resumed in Rafah, killing at least 40 people and wounding more than 150, medics said.
Prime Minister Benjamin Netanyahu's office accused Hamas and other Gaza militants of "flagrantly violating" the ceasefire.
Hamas spokesman Fawzi Barhum riposted that "it is the (Israeli) occupation which violated the ceasefire. The Palestinian resistance acted based on... the right to self defence."
Netanyahu's office said the premier spoke to Kerry by phone and said the Palestinians "unilaterally and grossly violated the humanitarian ceasefire and attacked our soldiers after 09:00".
The statement said Netanyahu warned that Hamas and "the other terrorist organisations in the Gaza Strip will bear the consequences of their actions".
Washington blamed Hamas for the breakdown of the ceasefire and accused it of launching a "barbaric" attack to capture the Israeli soldier.
"This is an outrageous action and we look to the rest of the world to join us in condemning it," White House Deputy National Security Adviser Tony Blinken told MSNBC television.
AFP correspondents reported fighting in the Rafah area.
The army warned people to remain at home, 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.
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.
- '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 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 denounced "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," he said.
"This silence is inexcusable" and will "result in a generation that rejects peace and believes only in violence," he said.
The truce came 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.