Hopes of an end to the bloodshed in Gaza rose early Friday after US Secretary of State John Kerry announced that Israel and Hamas had agreed a 72-hour ceasefire.

Both sides swiftly confirmed that they agreed to the ceasefire, due to begin at 0500 GMT Friday, after 25 days of bloody confrontation.

Speaking in New Delhi, Kerry said after the ceasefire went into force, Israeli and Palestinian representatives, including from Hamas, would begin talks in Cairo in a move confirmed by Egypt.

But he said Israeli forces would remain inside Gaza.

Earlier Thursday, Israel vowed it would not accept any ceasefire that did not allow troops to continue destroying tunnels used by militants to attack Israel.

The announcement came as the Palestinian death toll in Gaza hit 1,442, surpassing that of a massive three-week Israeli operation over New Year 2009, medics said.

UN figures show that around two-thirds of the victims were civilians, drawing sharp criticism from around the world.

The truce was a joint US-UN initiative and will give civilians "a much needed reprieve," Kerry said.

"This is a respite, a moment of opportunity -- not an end. It's not a solution," he warned, saying Israel would still be allowed to carry out "defensive" operations to destroy tunnels.

The proposal was accepted by Hamas, with a spokesman stressing it was dependent on Israel reciprocating.

"Hamas and all the resistance movements have accepted a 72-hour humanitarian ceasefire  from 8:00am Friday which will be respected by all these movements if the other party also observes the ceasefire," Fawzi Barhum said

"Israel has accepted the US/UN proposal for a 72-hour humanitarian ceasefire beginning 8:00am Friday (local time)," a source in the prime minister's office said.  

The announcement came after the UN Security Council expressed "grave disappointment" that repeated calls for a truce had not been heeded, and demanded there be a series of humanitarian breaks to ease conditions for civilians trapped in the war-torn territory.

Earlier, Israeli Prime Minister Benjamin Netanyahu vowed he would "not accept any proposal" that did not allow the army to complete its work destroying the tunnels.

"Until now, we have destroyed dozens of terror tunnels and we are determined to finish this mission -- with or without a ceasefire," he said, with the army's top commander for the Gaza area saying troops were "just days" away from completing the mission.

Despite rising international concern over the civilian death toll in Gaza, Washington said it had agreed to restock Israel's dwindling munitions supplies.

The announcement came as the White House said there was little doubt that 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 over 3,000 Palestinians made homeless by the relentless fighting which on Friday entered its 25th day.

"It does not appear there's a lot of doubt about whose artillery was involved in this incident," spokesman Josh Earnest said.

The Israeli army has suggested the deaths may have been the result of a misfired Palestinian rocket.

The European Union also condemned the hit on the school, saying it was "unacceptable" that those who had been forced out of their homes by the fighting - and at the request of the Israeli army - had been killed.

"These incidents must be investigated with immediate effect," it said.

With one in seven people of Gaza's population of 1.8 million people forced to flee their homes due to the intensive fighting, the UN agency for Palestinians refugees, which is sheltering almost all of them, warned it was stretched to breaking point.

"I believe the population is facing a precipice and appeal to the international community to take the steps necessary to address this extreme situation," UNRWA Commissioner General Pierre Kr?henb?hl told the Security Council.

There was no let-up Thursday in the bloodshed with at least 50 Palestinians killed, another 14 dying from injuries suffered in earlier attacks and a growing number of bodies pulled from under rubble in areas near Khan Yunis, medics said.

Eleven were killed in an Israeli air strike on a house in the central Gaza Strip's Nusseirat refugee camp, while three more were killed in night-time strikes in the south of the strip, and a body was recovered from rubble in the town of Khan Yunis

In Israel, 56 soldiers have died and Hamas rocket fire has killed three civilians, two Israelis and a Thai farmworker. (AFP)