Khamis Alawi, 44, huddled with his wife and six children in their kitchen as the IDF pushed past their home in Gaza City's northern Sheikh Ajleen neighborhood early Sunday morning. Bullets from the fighting outside came through their windows and riddled their walls. At a Jerusalem press conference on Sunday, UN officials warned that if Israel expanded its offensive, things would only get worse for the Alawis and the 1.4 million other people in Gaza, who had no place to flee. It would also be more difficult to distribute food and medical services, the officials said. "The protection of civilians will be further jeopardized and our staff will face further dangers," Filippo Grandi, the United Nations Relief and Works Agency's deputy commissioner, told journalists. According to the UN, as of 3 p.m. Sunday, 884 Gazans had been killed in Operation Cast Lead, including 275 children, 93 women and 12 medical personnel. In addition, 3,860 people had been injured, including 1,333 children and 587 women. The UN based its figures on information provided by Hamas's Health Ministry in Gaza. UNRWA is currently supporting 26,000 Gazans in 31 shelters, said Maxwell Gaylard, the UN's humanitarian coordinator in the Palestinian territories. But a much greater number had taken refuge with other families, he added. While the IDF has urged residents of Gaza City to flee the area, they had nowhere to go because the Strip's borders were closed, Gaylard said. Israeli military fire endangered their lives and made it difficult to provide them with necessary services, he said. Transporting patients and supplies to hospitals was dangerous, said Gaylard, who added that three ambulances and three mobile clinics had been damaged by gunfire. "People are hungry, they are cold, they have no electricity, they have no water," he said. "It is a massive crisis by any standard." Every day since Wednesday, Israel has suspended its operations during a three-hour window to allow the UN and other humanitarian agencies distribute food and medicine. Still, UNRWA claims that on Thursday its personnel were twice fired on by the army, and that in the second incident a Palestinian driver who was a contractor for its organization was killed by IDF gunfire. The IDF denied killing the truck driver. In an effort to prevent such incidents and to improve coordination, IDF officers met with officials from UNRWA and the International Red Cross on Sunday. In addition, the army let 91 truckloads of humanitarian aid into Gaza. To increase the flow of humanitarian supplies, the IDF is looking to open the Erez crossing into northern Gaza and the wheat chute at the Karni crossing farther south. At present the only open crossing is at Kerem Shalom, which has a limited capacity. Given the lack of supplies and the difficulties in distributing them, there is a shortage of flour, cooking gas, clean water and cash, said Gaylard. "We remain deeply concerned regarding the risks of epidemic outbreaks resulting from the discontinuation of vaccinations, garbage pileups and poor and unsafe drinking water," he said. Hospital continue to be overburdened. Doctors are working 24-hour shifts and intensive care units are full, he said. Both Gaylard and Grandi said that what was needed was an immediate cease-fire. "As long as the hostilities continue, civilians remain unprotected and more will be killed and injured," Gaylard said. "For every day the hostilities continue the cost to the civilian population intensifies." AP contributed to this report.