After initially rejecting the truce, Hamas spokesman Sami Abu Zuhri said in a statement, "As a preparation for the end of Ramadan and in response to the UN mediation and also regarding our people's living circumstances, we have agreed with all Palestinian factions to give a 24-hour humanitarian ceasefire starting from 14:00 on Sunday."
Israel had earlier extended the true which was announced on Saturday by another 24 hours but Hamas had rejected it saying that no ceasefire is valid without Israeli troops and tanks withdrawing from Gaza and that it would only halt rocket attacks on Israel once the displaced were allowed to return home.
Both sides accused each other of violating the ceasefire.
Hamas militants began firing rockets again this afternoon, blaming a "lack of commitment" from Israel.
The Qassam Brigades said on its websites it launched five rockets at Kiryat Gat. The announcement coincided with an Israel Defense Forces tweet that said it intercepted four rockets and one hit an open area. Another rocket today hit a house, slightly wounding an Israeli civilian.
Israel said that it had resumed its offensive because it was still being attacked.
"Following Hamas' incessant rocket fire throughout the humanitarian window, which was agreed upon for the welfare of the civilian population in Gaza, the IDF will now resume its aerial, naval and ground activity in the Gaza Strip," the IDF said.
Israel's Prime Minister Benjamin Netanyahu also accused Hamas of violating the ceasefire that it had itself called and vowed that Israeli operations in Gaza would go on.
"They (Hamas) are violating their own ceasefire. Under these circumstances, Israel will do what it must do to defend its people," Netanyahu said.
During the original 12-hour ceasefire, Palestinians frantically scoured through rubble with medics saying over 130 bodies had been retrieved across the Gaza Strip.
The Health Ministry in Gaza said that over 1,060 Palestinians, mostly civilians, have been killed and about 6,000 wounded since Israel launched its Gaza offensive on July 8.
Meanwhile, 46 Israelis have been killed in the fighting in the Gaza Strip aimed at ending rocket fire against Israel and destroying a sophisticated network of cross-border tunnels.

Sergeant First Class Barak Refael Degorker, a 27-year-old Indian-origin reservist, was among the dead.

Meanwhile, the Israeli army confirmed firing a mortar round into a Gaza UN shelter where 15 people died on Thursday, but denied killing anyone at the site.
"A single errant mortar (round) landed in the courtyard of the school," spokesman Lieutenant Colonel Peter Lerner said. "The courtyard was completely empty" at the time of the incident," he said.
"We reject the claims that were made by various officials immediately following the incident, that people were killed in the school premises as a result of (Israeli army) operational activity," he added.
At least 120,000 Palestinians have been displaced in the current round of violence and about 80 percent of the casualties have been civilians.
The UNICEF has said that 192 children had been killed during the conflict.
As the death toll continued to rise, Foreign Ministers from the US, Turkey, Qatar and several European countries urged both sides to extend the truce after their talks in
No representatives from Israel, Egypt or the Palestinian Authority attended the Paris talks.
US Secretary of State John Kerry also joined talks. Kerry met with Turkish Foreign Minister Ahmet Davutoglu.
Kerry had spent most of last week meeting officials in the Middle East to try to broker a more lasting end to the fighting. But so far, his efforts have not yielded desired results.
He returned to United States on Sunday.

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