Israeli shelling killed 43 Palestinians on Tuesday at a UN school where civilians had taken shelter, medical officials said. In another Israeli attack on civilians, at least 12 members of the same extended family, including seven children, were killed when their three-story house in Gaza City was reduced to rubble in an airstrike. UN Secretary-General Ban Ki-moon said it was “totally unacceptable” that Israel would attack any of the United Nation's 23 Gaza schools where some 15,000 Palestinians whose homes were destroyed or who were fleeing the violence had sought refuge. The UN has provided the Israeli military with GPS coordinates for all of them to ensure that their buildings in Gaza are not targeted. Israeli Foreign Minister Tzipi Livni said about the deaths: “Unfortunately, (Hamas fighters) are hiding amongst civilians.” The Israeli army said its troops had fired mortars at the premises after gunmen mortared their positions from inside Al-Fakhora school in Jabalya refugee camp. Citing intelligence reports, it named two men it said were Hamas gunmen killed in the attack. A spokesman said the army did not know how many others died. “There's nowhere safe in Gaza. Everyone here is terrorized and traumatized,” said John Ging, the top UN official in Gaza. People cut down by shrapnel lay in pools of blood in the street. Witnesses said two shells exploded outside the school, killing at least 43 civilians and wounding dozens among people who had taken refuge there and residents of nearby buildings. Israel's shells have fallen around at least three schools and a health center run by the UN for Palestinian refugees. As bitter combat on the ground went into a fourth day after a week-long aerial bombardment, the bloodshed took Palestinian deaths in 11 days of violence to 660, including 215 children and 98 women. Another 2,950 people have been wounded. Seven Israeli soldiers have been killed during Operation Cast Lead, while three civilians were killed in Israel by rockets fired by Gaza militants, according to the army. Tuesday's spike in civilian casualties could prove to be a turning point in Israel's “Operation Cast Lead”, launched on Dec. 27 with the declared aim of removing the Hamas rocket threat. The killing of 28 unarmed Lebanese in Israeli bombing in the village of Qana in the 2006 Lebanon war drained foreign support for its campaign against Hezbollah guerrillas. In fighting Tuesday, Israeli forces pushed into the southern town of Khan Younis and battled Hamas militants on the outskirts of the city of Gaza. Arab governments have condemned the Israeli assault, which has contributed to rising oil prices Venezuelan President Hugo Chavez, an OPEC member, called it a “holocaust” and expelled the Israeli ambassador from his country. “The Holocaust, that is what is happening right now in Gaza,” Chavez said in televised comments Tuesday. “The president of Israel at this moment should be taken to the International Criminal Court together with the President of the United States.”