Israel declared a Gaza ceasefire over today and killed more than 50 Palestinians in renewed shelling, saying militants had breached the truce shortly after it began and apparently captured an Israeli soldier.

The 72-hour break announced by US Secretary of State John Kerry and UN secretary general Ban Ki-moon was the most ambitious attempt so far to end more than three weeks of fighting, and followed mounting international alarm over a rising Palestinian civilian death toll.

The ceasefire was to be followed by Israeli-Palestinian negotiations in Cairo on a longer-term solution.

Egyptian officials said the invitation still stood, but some Palestinian representatives had asked for a postponement until tomorrow or Sunday to allow a new truce to be reached.

The Israeli military said that 90 minutes into the truce - as Palestinian families who had fled neighbourhoods that had been turned into battlefields began to trek home - militants attacked soldiers searching for infiltration tunnels in the southern Gaza Strip.

“Out of a tunnel access point or several, terrorists came out of the ground. At least one was a suicide terrorist who detonated himself. There was an exchange of fire,” said Lieutenant-Colonel Peter Lerner, a military spokesman. Two of the soldiers were killed.

“The initial indication suggests that a soldier has been abducted by terrorists during the incident,” he said in a conference call with reporters.

Asked if the ceasefire was over, Lerner replied: “Yes. We are continuing our activities on the ground.” He said Israeli forces were mounting an “extensive effort” to locate the soldier.

The Gaza health ministry said more than 50 people were killed and 220 wounded by Israeli shelling after the incident near the southern town of Rafah.

The truce had left Israeli ground forces in place in the Hamas-dominated Gaza Strip and a military spokeswoman had said operations would continue to destroy a warren of tunnels through which the Islamist group has menaced Israel’s southern towns and army bases.

There was no immediate word from militant groups on whether any were holding the soldier, identified by the military as Second Lieutenant Hadar Goldin (23). Sami Abu Zuhri, a spokesman for the dominant Hamas movement in Gaza, said Israel was trying to mislead the world and “cover up its Rafah massacre”.

Israel launched its offensive in Gaza on July 8th, unleashing air and naval bombardments in response to a surge of cross-border rocket attacks. Tanks and infantry pushed into the territory of 1.8 million on July 17th.

Gaza officials say at least 1,509 Palestinians, mostly civilians, have been killed and 7,000 wounded. Sixty-three Israeli soldiers have been killed and more than 400 hurt. Three civilians have been killed by Palestinian rockets in Israel.

Eight rockets and mortar bombs were fired from Gaza at Israel after the ceasefire began, the military said, adding that one was intercepted by the Iron Dome system and seven hit open areas.

Amid strong public support in Israel for the Gaza campaign, prime minister Benjamin Netanyahu had faced intense pressure from abroad to stand his forces down.

International calls for an end to the bloodshed intensified after shelling on Wednesday that killed 15 people sheltering in a UN-run school in Gaza’s Jabalya refugee camp.

Hamas, isolated in an Arab world concerned about the rise Islamist militancy, is seeking an end to Israel’s blockade of Gaza. It also wants a hostile Egypt to ease restrictions at its Rafah crossing with the territory imposed after the military toppled Islamist president Mohamed Mursi last July.

Israel has balked at freeing up Gaza’s borders under any de-escalation deal unless Hamas’s disarmament is also guaranteed.

Saudi Arabia’s King Abdullah has criticised international inaction over Israel’s offensive in Gaza, which he described as involving mass slaughter and “war crimes against humanity”, in a speech read out on his behalf on state television. “This (international) community which has observed silently what is happening in the whole region, was indifferent to what is happening, as if what is happening is not its concern. Silence that has no justification,” he said in his speech.

A senior State Department official travelling with Kerry in India had said US Deputy Secretary of State Bill Burns would arrive in Cairo tomorrow and that Frank Lowenstein, the acting US envoy for Middle East peace, and another US official, Jonathan Schwartz, would be there today.

Speaking before the renewed fighting, the official said he believed the Palestinians would be in Cairo on today, while the Israelis would arrive tomorrow. After the truce collapsed, two Egyptian officials said there had been no official cancellation of Cairo’s request for the negotiators to come.

The Palestinian delegation would be comprised of Hamas, Western-backed Fatah, the Islamic Jihad militant group and a number of smaller factions, Palestinian officials said.

But US officials said Israel and the United States would not sit across the table from Hamas, which the two countries, along with the European Union, consider a terrorist group.

Reuters