The Israeli military has been forced to retract a statement claiming that the mortar shell that killed a four-year-old Israeli boy on Friday was fired from or near a United Nations school in Gaza.

After the death of Daniel Tragerman outside his home in a kibbutz near the Israel-Gaza border, a spokesman for the Israel Defence Forces (IDF) said the mortar was fired from or near a school run by UNRWA, the UN agency for Palestinian refugees, which was being used to shelter Palestinians who have fled their homes because of bombing and destruction.

A correction later tweeted by an IDF spokesperson, Peter Lerner, read: "After further review, the school the mortar was launched near from is not being used as a shelter by UNRWA but rather a shelter maintained by Hamas authorities in Gaza."

UNRWA has become embroiled in the Israel-Hamas conflict after at least six of its schools being used as shelters were hit by Israeli air strikes or shelling, and Hamas arms caches were found at three disused schools.

In a statement UNRWA said it "deplores the killing of all children during this conflict, including the killing of the four-year-old Israeli child … and the hundreds of Palestinian children killed since the start of the current fighting. We call on all parties to ensure protection and care of children affected by armed conflict, in accordance with their obligations under international law."

In Cairo, the Palestinian president, Mahmoud Abbas, said talks aimed at ending the war between Gaza and Israel should restart as soon as possible. His comments came four days after fighting resumed following the breakdown of the latest in a series of temporary ceasefires.

"My main goal is for the truce talks to resume in Egypt as soon as possible to avoid more casualties and sacrifices," Abbas told reporters after meeting the Egyptian president, Abdel Fattah al-Sisi. Palestinian and Egyptian officials in Cairo said no new talks had been scheduled.

Military activity continued, with rockets launched from Gaza and air strikes carried out by the IDF. Gaza residents were warned in text messages, automated phone calls and leaflets dropped from the air that Israel's military campaign was not over, and to "stay away from every site in which terrorist organisations are operating".

A senior Hamas official said the organisation would not sign up for any more temporary ceasefires. "Our primary efforts are now focused on international and European attempts to reach a long-term truce between the sides," Moussa Abu Marzouk told Al-Jazeera.

British, French and German diplomats at the United Nations in New York have drafted a framework for a long-term ceasefire agreement, which could form the basis of a security council resolution. It attempts to address Palestinian demands for an end to the blockade of Gaza and Israel's security concerns.

Hamas announced it had backed a Palestinian move to join the nternational criminal court (ICC), the first step in taking legal action against Israel for alleged war crimes.

"Hamas signed the document which [Abbas] put forth as a condition that all factions approve, before he goes to sign the Rome Statute, which paves the way for Palestine's membership in the international criminal court," Marzouk wrote on his Facebook page.

Israel vehemently opposes Palestinian membership of the ICC, and many international diplomats warn that such a move could be counterproductive in entrenching Israel's aversion to resuming the stalled Middle East peace process.

It could also expose Hamas to scrutiny by the ICC. A UN investigation into the last conflict in Gaza, Operation Cast Lead in 2008-09, concluded that both Israel and Hamas committed war crimes.

Izzat Rishq, a senior Hamas official, said the organisation was not concerned about becoming the target of a war crimes investigation, and urged Abbas to act as soon as possible.

"We are under occupation, under daily attack, and our fighters are defending their people," he told the Associated Press. "These rockets are meant to stop Israeli attacks and it is well known that Israel initiated this war and previous wars."