Palestinian civilians in Gaza have no place to hide from Israel's military offensive and children are paying the highest price, the United Nations said Tuesday. "There is literally no safe place for civilians," Jens Laerke, spokesman of the U.N. Office for Humanitarian Assistance (OCHA), told reporters in Geneva. According to Laerke, more than 500 people have been killed in the coastal enclave that has an estimated 4,500 people per square kilometer. The priority for aid agencies was protecting civilians and evacuating and treating the wounded. Nearly 500 homes have been destroyed by Israeli air strikes and 100,000 people have sought shelter in schools of the U.N. Relief and Works Agency (UNRWA), where they need food, water, and mattresses, the OCHA spokesman said. So far, 29 Israelis – 27 of them soldiers – have died. But the overwhelming majority of people killed so far in the latest outbreak of violence are Palestinians, including 121 Gaza children under the age of 18 who make up one-third of the total civilian casualties, Juliette Touma of the U.N. Children's Fund (UNICEF) said. More than 900 Palestinian children are also reported to have been injured, UNICEF said. "According to an assessment by aid workers on ground at least 107,000 children need psycho-social support for the trauma they are experiencing such as death, injury, or loss of their homes," Laerke said. More than 1.2 million people in the enclave have no water or only limited access to water as power networks have been damaged or lack fuel for generators, Laerke said. "In addition, we do have reports of sewage flooding which is a threat to public health," Laerke said. The World Food Programme (WFP) has distributed emergency food rations and food vouchers to more than 90,000 people so far during the conflict, spokeswoman Elisabeth Byrs said. "Ready to eat food stocks are running low in Gaza given the conflict has lasted two weeks and the needs are increasing," Byrs said. The World Health Organization (WHO) said that 18 health facilities in Gaza have been damaged, including three hospitals.