Despite air strikes that have hit several buildings in the city centre, hundreds of refugees still flock to Tyre every day, fleeing fighting in the border villages to the east. They usually stay one night in one of the city's hotels, before trying to find a way to go north in search of safety. "My parents don't know where I am... I want to reassure my family that we are all well," Wafa, who came to Tyre the night before, said. The U.N. estimates there are up to 800,000 people in Lebanon displaced by the fighting and bombing. It said there are nearly 600 schools being used as shelters, with between 100 and 1,200 people in each school. In Tyre, some soldiers of the 2,000 strong United Nations Interim Force in Lebanon (UNIFIL) took position on the streets near the hotel. UNIFIL operated more than 40 U.N. outposts along the Israeli border. Four posts are now unoccupied as the United Nations withdrew its peacekeepers after Israel attacked a base in Khiam on Tuesday (July 25) and killed four unarmed U.N. observers. The four dead were part of the U.N. Truce Supervision Organisation, a unit of about 155 observers under the command of the UNIFIL. UNIFIL's mandate expires on Monday (July 31). On Friday (July 28), Israeli warplanes and artillery pounded villages near Lebanon's southern port of Tyre, killing at least 13 people, while four more died in air strikes in the eastern Bekaa valley. The United Nations has been running aid convoys to towns in southern Lebanon, such as Tyre, Sidon and Jezzine, but getting food and medical supplies safely to the towns and villages at the heart of the fighting is proving difficult. In Beirut, a U.S. warship carrying humanitarian aid, including medicine, to areas badly affected by almost three weeks of Israeli bombardment, arrived on Saturday (July 29). The aid will be sent to Shuf Mountain, 40 kilometres south of Beirut, a spokeswoman for MeryCorps, an international humanitarian aid and development organisation, said. About 20,000 blankets, seven medical kits and hundreds of boxes of medicine were unloaded under heavy U.S. security. Cassandra Nelson said that more aid would be sent in coming days and they aim to deliver it to southern Lebanon, which has seen some of the worse fighting. She said that one of their biggest concerns is ensuring that isolated villages receive drinking water. "We've already seen in some of these areas outbreak of diarrhoea in small children and we are very concerned about the escalating health crisis from water borne illnesses, things can result in hepatitis, and different kinds of diseases that can really effect the most vulnerable of the population, children, nursing mothers and the elderly," Nelson said. The United States said it would contribute 30 million dollars (USD), including medical kits for 100,000 people, 20,000 blankets and plastic sheeting. The U.S. Agency for International Development (USAID) announced it would distribute more than 7 million dollars (USD) in humanitarian assistance to numerous U.N. agencies.