GAZA - Israel's intensified bombardment on the Gaza Strip and a threat of ground assault have met with strong objections from the international community, including the West.

An Israeli bomb fell upon al-Dalou family's two-storey house in Gaza City's residential al-Nasser neighborhood on Sunday, killing 11, including four children and a woman as old as 81, and reducing the structure to bubbles. It was one of the deadliest event in five days of conflict between Israel and Gazan militants.

The air strike, termed by Prime Minister of the de facto Hamas government Ismail Haneya as "an awful massacre," came after Israel pledged to broaden and intensify assault on the Gaza Strip from military homes to government infrastructure.

A four-story headquarters of the leading Hamas officials were eliminated with a barrage of five bombs before dawn on Saturday, and more than a dozen homes linked to Hamas were struck a day later, three of which were inhabited.

Since the start of the Operation Pillar of Defense on Wednesday, Israel has killed 72 Palestinians, including 20 children, eight women and nine old men, and injured more than 600 others, Palestinian medical sources said.

At the meantime, Israeli ground troops and armored vehicles continued to build up along the border with the Gaza Strip on Sunday in the face of unusually strong Palestinian fire.

Armed with long-range and surface-to-air missiles, militants of the coastal enclave fired 120 rockets to Israel on Sunday along, wounding 14 people. Sirens sounded in Tel Aviv which came under rocket attacks for the first time since the 1991 Gulf War.

Israeli Vice Prime Minister Moshe Yaalon had said "regarding operational considerations we should be ready to deploy whatever is needed to reach peace and quiet. So far we tried to make it, to achieve it, by surgical airstrikes, but we should be ready to deploy more troops in different types of operations in order to reach this goal (of peace)." His remarks fueled speculations of a ground assault.

The International community, even the West, moved quickly to oppose Israeli ferocity and threats.

US President Barack Obama, who has been touring Southeast Asia, called on Israel to refrain from a ground operation, saying the move could endanger the lives of Palestinian civilians as well as Israeli soldiers, and hamper the shaky peace process.

"If we see a further escalation of the situation in Gaza, the likelihood of us getting back on any kind of peace track that leads to a two-state solution is going to be pushed off way into the future," he said.

British Foreign Secretary William Hague, whose government had blamed mainly the Hamas movement for the ongoing conflict, said "a ground invasion of Gaza would lose Israel a lot of the international support and sympathy that they have in this situation."

French Foreign Minister Laurent Fabius who had carried out a truce tour of the region, said "war is not an option, it is never an option," highlighting "urgency" and "ceasefire."

UN Secretary-General Ban Ki-moon on Sunday strongly urged Israel and Palestinian militants "to cooperate with all efforts led by Egypt to reach an immediate cease."

"Any further escalation will inevitably increase the suffering of the affected civilian populations and must be avoided," he said.

However, Canadian Defence Minister Peter Mackay said Sunday that between 500 and 600 rockets had rained down on Israel from the Hamas-controlled Gaza, and that Israel "has the right to defend itself" against such attacks, one of the few supportive voice left for Israel.