Israeli warplanes and combat helicopters dropped more than 100 tons of bombs on the Hamas-ruled Gaza Strip on Saturday, killing at least 228 people and wounding more than 700 others in one of the bloodiest days for Palestinians in more than 60 years. Medical workers said there were many civilian casualties. As an Israeli military spokesman warned that the mid-morning bombardment was “just the beginning,” Hamas threatened to unleash “hell,” calling on its fighters to “avenge with force against the enemy” and warning Israelis living near the border to “prepare the funeral shrouds.” The bombardments hit and destroyed Hamas security structures across the Gaza Strip, the group said. A training base of its military wing, the Ezzedine Al-Qassam Brigades, was pounded in the north of the territory. Five senior Hamas officials were said to have been killed. Among them were the Hamas-appointed police chief, Tawfiq Jabber, the head of Hamas's security and protection unit, and the governor of central Gaza, according to medical workers. Hamas responded with rocket salvoes that killed an Israeli man and wounded several others, medics said. At the main police headquarters, some rescue workers beat their heads and shouted “God is greatest” as one badly wounded man lying nearby quietly recited verses from the Qur'an. The Israeli military said it had targeted “terrorist infrastructure” following days of rocket attacks from Gaza on Israel and pledged more strikes if necessary, possibly targeting Hamas leaders. Palestinian President Mahmoud Abbas said in Riyadh that he was in “urgent contact” with numerous countries to stop “the cowardly aggressions and massacres in the Gaza Strip.” The bombardment sparked international calls for a stop to the violence, with the Arab World, Russia, France and the European Union calling for an end to the bloodletting by both sides. The US typically took the position that Israel has the right to defend itself. Egypt, which brokered a six-month Israeli-Hamas truce that expired on December 19, slammed the Israeli strikes. “Egypt condemns the Israeli military aggression on the Gaza Strip and blames Israel, as an occupying force, for the victims and the wounded,” President Hosni Mubarak said in a statement. He gave instructions for the Rafah terminal – the only one that bypasses Israel – to be opened to allow wounded Palestinians to be evacuated “so they can receive the necessary treatment in Saturday's deadly attacks came after days of escalating violence around the besieged coastal strip that the Hamas movement has run since June 2007, with militants firing rockets and Israel vowing a fiery response. A shaky Egyptian-brokered truce between Israel and Hamas started to break down in early November. Hamas had originally agreed to a six-month lull, and declared it officially over when the six-month period expired on Dec. 19. Asked if an escalation of the assault could include targeted strikes against Hamas leaders, army spokeswoman Avital Leibovitch said: “Anything belonging to Hamas could be a target. You can interpret that as you like.” A five-day Israeli offensive in March killed more than 120 people, but Saturday's death toll would be the highest for Palestinians since their 1980s uprising.