Regional security is at risk if the international community does not tackle the Syrian refugee crisis, the United Nations warned on Thursday.Antonio Guterres, the UN High Commissioner for Refugees, said the UN is aiming to raise $3.74 billion from member states to help protect vulnerable refugees in Turkey, Jordan, Lebanon, Iraq and Egypt."The international community simply cannot afford to let this growing and increasingly protracted population of refugees fall through the cracks," Guterres said. "Nor can we fail to support the countries who generously host them."The UN estimates at least 2.9 million Syrian refugees are registered across the region. This figure is growing at a rate of 100,000 a month, according to the refugee agency. An increasing number of women and children among them are facing "violence, exploitation and abuse."The UN has repeated its concerns that Syrian refugees also face reduced food rations, raising the possibility of widespread malnutrition.Due to poor hygiene conditions and a lack of access to clean water, Syrian families may also be at risk from diarrhea, typhoid, polio and other water-borne and contagious disease, the UN added. Valerie Amos, Emergency Relief Coordinator for Humanitarian Affairs at the UN, "remains deeply concerned" about the humanitarian situation in Iraq, "where families urgently need assistance and children are vulnerable to outbreaks of disease and malnutrition," UN chief spokesperson Stephane Dujarric said.