People shout slogans as they demonstrate to denounce Israeli air strikes on the Gaza strip, in Sanaa July 10, 2014. [Photo/Agencies]

GAZA/JERUSALEM - As of Thursday afternoon, the Israeli Air Force struck down about 800 targets in the Gaza Strip, killing at least 80 Palestinians, including 22 children, 15 women and 12 elderly, Palestinian medical sources report. More than 500 people were injured in the attacks.

Tensions in Gaza draw int'l concern as Israeli strike continues Children under air strike in Gaza

Since the operation started, hundreds of rockets and mortars were launched towards Israel, including cities in Israel's central, south central plain and the northern plain area, as well as in the Jerusalem greater area and southern communities.

As Israeli officials seemed to hint at a possible invasion by ground forces, eight members of one family, including five children, were killed in an early morning air strike that levelled two homes at Khan Younis in the south of the Gaza Strip near the Egyptian border, the Palestinian Health ministry said.

Israel's military made no comment on what would be the deadliest strike since its began its assault on Tuesday. The defence minister spoke of "long days of fighting ahead".

US President Barack Obama told Israeli Prime Minister Benjamin Netanyahu in a phone call that the United States was willing to help negotiate a ceasefire, the White House said.

French President Francois Hollande voiced his concern at the civilian deaths in the Palestinian enclave and called for a truce. A spokeswoman for US Secretary of State John Kerry, who like Hollande spoke to Palestinian President Mahmoud Abbas, said of possible escalation: "Nobody wants to see a ground invasion."

The offensive followed a build-up in violence after three Jewish students were killed in the occupied West Bank last month and a Palestinian youth died in a suspected revenge attack.

Netanyahu said in a televised statement: "So far the battle is progressing as planned but we can expect further stages in future. Up to now, we have hit Hamas and the terror organisations hard and as the battle continues we will increase strikes at them."

Netanyahu discussed options with his security cabinet as air strikes continued and officials hinted at a possible ground offensive. There was no word on when or if this would happen.