Eleven civilians, including nine members of a family, were killed Sunday in the deadliest single strike by the Israeli air force since the cross-border firing started Wednesday between the Palestine Hamas and Israel in the Gaza strip, news agencies reported.

Civilian death toll rose as Israel airstrikes targeted the densely populated Gaza strip Sunday amid calls from international leaders to halt the cross-border assault. 

Israeli aircraft bombed a three-storey building, home to shop owner Jamal Dalu and his family, killing eleven, including four women and four children.

The building was leveled and the entire Dalu family, except Jamal Dalu, perished under the rubble. Dalu escaped unhurt as he was at a neighbor’s home during the incident. It took hours for emergency workers to recover the bodies of Dalu’s sister, wife, two daughters, daughter-in-law, four grandchildren between the ages of two and six and his two neighbors, according to a New York Times report.

Israel's chief military spokesman told the country's Channel 2 television that Yihia Abayah, a senior commander of Hamas, had been the target of the attack and admitted that there were civilian casualties from the attack. He said that Israeli military was "examining the event.”

The civilian deaths were condemned widely as pressure mounted to end the cross-firing that had claimed 78 lives, of which 23 are those of children, in Palestine since the latest offensive began.

United Nations Secretary General Ban Ki-moon, who will visit Israel Tuesday, expressed concern over the civilian deaths.

"I am deeply saddened by the reported deaths of more than ten members of the Dalu family... (and) by the continuing firing of rockets against Israeli towns, which have killed several Israeli civilians. I strongly urge the parties to cooperate with all efforts led by Egypt to reach an immediate ceasefire," he said, as reported by Reuters.

Israel widened its air campaign against the Palestinian militant targets in Gaza Sunday. The Israeli offensive started six days ago after the Hamas militants had fired rockets into Israel targeting Jerusalem and Tel Aviv.

Cross-firing continued throughout Sunday, even as attempts to end hostilities between Gaza and Israel continued with negotiators holding talks with both the sides. Hundreds of rockets were fired toward Israel and most of them were intercepted by Israel’s Iron Dome anti-missile defense system.

According to the Israeli military, 544 rockets fired from Gaza have hit Israel since Wednesday. About 302 rockets were intercepted by the Iron Dome and 99 failed to reach Israel and landed inside the Gaza Strip.

Peace Talks Progress As International Pressure Mounts

Efforts to end the current cross-firing saw some progress as both Palestine and Israel said ceasefire might be achieved if both sides agreed to each other’s conditions.

Egypt has taken the lead in the negotiations and is holding continuous talks with different factions in the Palestine government and Israel.

Egyptian President Mohamed Mursi met Khaled Meshaal, the political leader of Hamas, and Ramadan Shallah of Islamic Jihad, while an Israeli delegation had been to Cairo to participate in the talks to end the airstrikes, news agencies reported. Mashaal also met Turkish Prime Minister Tayyip Erdogan Sunday.

Ban Ki-moon is also expected to arrive in Cairo this week to push forward peace talks.

A Facebook post by Izzat Risheq, a close aide of Meshaal, said that the truce efforts were on, but they had not concluded with a positive decision.  He wrote to agree to a ceasefire: “we must achieve the conditions of the resistance and the goals of our people… to stop the (Israeli) aggression and the policy of assassinations and end the unjust siege on Gaza.”

Vice Prime Minister of Israel Moshe Ya'alon said in his Twitter post that Israeli strikes would stop only when rockets from Gaza ceased firing.

“If you will be quiet in the south and the Gaza Strip (and) will not fire missiles and rockets on Israeli civilians and IDF soldiers then there will be not attacks,” Ya'alon said.