At least three people have been killed in an Israeli bombing raid on a United Nations school in the Gaza Strip. Hundreds of terrified Palestinians were taking shelter in the building after fleeing fierce fighting between Israeli soldiers and Hamas fighters. The latest fatalities in the 11-day-old conflict come after Israel warned that fighting in Gaza could get worse before its mission against Hamas is complete. Palestinian witnesses said Israeli forces have pushed into Khan Younis in southern Gaza as the army widened the ground assault it launched four days ago against Hamas militants. At least 718 Palestinians, including 130 militants, have been killed since the offensive began. In the latest attacks, at least 35 people are reported to have died. The dead included ten killed by naval shells along the beach in the central Gaza Strip and 11 people, including five children, whose bodies were pulled from the rubble of a house hit by an airstrike. Nine Israelis, including three civilians hit in Palestinian rocket attacks, have died in the conflict. Many of the Gaza Strip's 1.5 million people lack food, water or power and hospitals are struggling to cope with the casualties of the conflict. Save the Children has called for aid to be let in to the stricken area and said that 50,000 children are already suffering from chronic malnutrition. More than 2,000 families were displaced prior to the launch of the ground offensive on Saturday with charities expecting the number to increase significantly as fighting escalates. Politicians led by Prime Minister Gordon Brown have united to urge both sides to reach an immediate ceasefire. Mr Brown said it was vital that the international community, including the Arab League, worked together to find a workable solution to the problem. He said: "This is a very dangerous moment, I think everybody around the world is expressing grave concern. What we've got to do almost immediately is to work harder than we've done for an immediate ceasefire." US President George W Bush has insisted that any ceasefire to end the Gaza crisis must include provisions to prevent Hamas from continuing to use the coastal strip to fire rockets into Israel. Mr Bush made it clear while he is concerned about deteriorating conditions for Palestinians living in Gaza that he puts the onus on Hamas. He stopped short of calling for an immediate halt to the fighting as some European leaders have done.