Israel accepted an Egyptian proposal to hold fire Tuesday after a week-long campaign in Gaza, but warned Hamas it would hit back even harder if the rocket fire does not stop.
In an early-morning vote, Israel's security cabinet said it would accept an Egyptian ceasefire which went into force at 0600 GMT, despite Hamas rejecting the initiative.
But the calm was short-lived, with sirens sending tens of thousands running for cover along Israel's Mediterranean coast as militants fired rockets at the densely-populated plain.
The army said one was even fired at the port city of Haifa, 165 kilometres (102 miles) to the north, although there was no confirmation of anything landing there.
The truce proposal, which Cairo laid out late Monday, won US support as the death toll in Gaza soared to 192 after a week of intensive bombardment by the Israeli air force.
But the Islamist Hamas movement, whose militants have fired more than 1,000 rockets, ruled out any end to the fighting without a full agreement.
And tensions rose along Israel's other frontiers, with three rockets hitting in and around the southern resort city of Eilat overnight after another fired from Lebanon struck just outside the northern coastal town of Nahariya, the army said.
A rocket fired from the Syrian Golan also struck the Israeli-occupied sector, prompting the air force to launch a pre-dawn strike, killing four, said the Syrian Observatory for Human Rights.
As the violence resumed, with 35 rockets striking Israel since the 0600 GMT deadline, Israeli Prime Minister Benjamin Netanyahu warned Hamas the Jewish state would not hesitate resume its punishing campaign in and around Gaza.
- Gaza demilitarisation -
"We responded positively to the Egyptian proposal to give a chance to deal with the demilitarisation of Gaza," Netanyahu said, referring to Hamas's arsenal of missiles and rockets.
"But if Hamas doesn't accept the ceasefire proposal -- and that's how it seems at this point in time -- Israel will have all the international legitimacy to broaden its military activity in order to achieve the necessary quiet."
Cairo's initiative was made after Washington warned Israel against a launching a ground offensive in Gaza, where troops and military hardware have massed along the border.
"We are encouraged that Egypt has made a proposal to accomplish this goal that we hope can restore the calm that we are seeking," said US President Barack Obama, as Secretary of State John Kerry warned of the "great risks" of any new escalation.
German Foreign Minister Frank-Walter Steinmeier also urged Hamas to accept the Egyptian proposal, accusing the Islamists of holding the people of Gaza "hostage".
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And Israeli President Shimon Peres said a ceasefire must mean an end to rocket fire on Israel.
"We all wish to lower the flames, we want an end to the fighting and we hope to see it soon. But there can be no compromise with terror. A ceasefire must be on these terms: No more rockets. No more terror."
But Turkish Prime Minister Recep Tayyip Erdogan put the blame entirely on Israel accusing it of carrying out "state terrorism" and a "massacre" of Palestinians in Gaza.
- 'Respond with force' -
Israel's security cabinet approved the Egyptian proposal by six votes to two, ordering the military to halt its fire.
"Israel's leadership has directed our forces to suspend strikes in Gaza," the army tweeted. "If Hamas fires at Israel, we will respond with force."
On the ground, Gaza's streets were a little fuller than in previous days, with people taking advantage of the unilateral ceasefire to escape their homes and stock up on provisions.
Despite the renewed rocket fire, there were no immediate reports from Gaza of the military hitting back.
Overnight, a Hamas official said there would be no truce without a fully-fledged deal on the table, and hours later, the movement said it had not been consulted.
"Because we were excluded from the consultations for this (truce) initiative, we are not obliged to abide by it," a statement said.
However, a top Hamas official said the movement had not yet formulated a position on the proposal.
"We're still in consultations. The movement has yet to take an official position on the initiative," Mussa Abu Marzuk, Hamas's overseas deputy based in Cairo, wrote on Facebook.
Israel launched Operation Protective Edge before dawn on July 8, hitting Gaza with an intensive aerial bombing campaign aimed at stamping out rocket fire.
Militants answered with over 1,000 rockets, dozens of which have targeted central and even northern Israel.
So far, the conflict has claimed 192 Palestinian lives, with rights groups saying well over two-thirds were civilians.
Over the same period, 882 rockets have struck Israel, and close to 200 have been shot down, the army said.