Gaza Strip: A Gaza ceasefire was in jeopardy just hours after it began on Friday, with the Islamist group Hamas saying Israeli tank fire killed four people and Israel accusing militants of violating the truce.
Some two hours after the truce went into effect, a Reuters photographer and the Gaza Interior Ministry said Israeli tanks opened fire in the southern Rafah area, and Hamas media reported 40 people were killed. The Israeli military had no immediate comment.
The 72-hour break announced in a joint statement 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.
Israel launched its offensive in Hamas Islamist-dominated Gaza on July 8, 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 17.
Gaza officials say at least 1,459 Palestinians, mostly civilians, have been killed and 7,000 wounded. Sixty-one Israeli soldiers have been killed and more than 400 wounded. Three civilians have been killed by Palestinian rockets in Israel.
An official in Israeli Prime Minister Benjamin Netanyahu's office said Hamas and other armed groups in the Gaza Strip had "flagrantly violated the ceasefire". But the official did not elaborate.
A local official in an Israeli southern border community said on Israel's Channel 10 television that sirens warning of rocket attacks had sounded. No casualties or damage were reported.
After the ceasefire began at 08:00 local time (0500 GMT), Gaza's streets began to fill with Palestinian families. Laden with belongings, they streamed back to homes they fled during fierce fighting that destroyed or damaged thousands of dwellings.
In Israel, sirens that have sent tens of thousands running for shelter daily fell silent.
"We are going back to Beit Lahiya (in the northern Gaza Strip)," said Asharaf Zayed, a 38-year-old father of four. "We hope the truce will be permanent and we won't have to go back to a U.N. shelter."
Amid strong public support in Israel for the Gaza campaign, Netanyahu had faced intense pressure from abroad to stand his forces down.
The truce left Israeli ground forces in place in the Gaza Strip and a military spokeswoman said operations were continuing to destroy a warren of tunnels through which Hamas has menaced Israel's southern towns and army bases.
"We are doing what needs to be done in order to neutralise them," she said.
Israel has balked at freeing up Gaza's borders under any de-escalation deal unless Hamas's disarmament is also guaranteed.
Israeli strikes killed 14 people in Gaza, including eight from one family, hospital officials said. Earlier, Hamas rockets set off sirens in the Tel Aviv area and one was intercepted.
Israel's military said five of its soldiers were killed late on Thursday by a mortar bomb.