The new move came after a crisis meeting of Israeli cabinet late on Saturday night. They extended the truce until midnight on Sunday. The cabinet also warned that the army will act if it is breached by Palestinian militants.
The Cabinet was to reconvene on Sunday to discuss the continuation of the military operation, the officials said.
But Hamas said in a statement that "no humanitarian ceasefire is valid without Israeli tanks withdrawing from the Gaza Strip and without residents being able to return to their homes and ambulances carrying bodies being able to freely move around in Gaza".
Israel and Hamas agreed to a 12-hour humanitarian truce on Saturday which the Jewish state later extended by four hours till midnight local time.
Israel said that it would continue operations against tunnels used by Hamas during the truce period.
But Hamas had fired several rockets at Israel from the Gaza Strip after the initial 12-hour truce ended and rejecting an earlier attempt to prolong the truce.
Meanwhile, Hamas also accused Israel of using previous ceasefires to prepare more attacks and claimed that there had been truce violations on Saturday.
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 discovery of the bodies under mounds of rubble had pushed the Palestinian death toll to over 1,000 in the coastal enclave since the conflict began on July 8.
About 5,870 Palestinians have been wounded in the 19-days of fighting, Gaza health officials say.
The original truce expired at 08:00 local time (17:00 GMT) on Saturday. Gazans had been using the pause to recover bodies and gather supplies.
About 5,870 Palestinians have been wounded in the 19 days of fighting, Gaza health officials say.
At least 120,000 Palestinians have been displaced in the current round of violence and about 80 per cent of the casualties have been civilians.
The UNICEF has said that 192 children had been killed during the conflict.


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