"We have lost the main entry point for humanitarian aid [Kerem Shalom]," Andrea De Domenico, head of the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) in the occupied Palestinian territories, told AFP. Israel closed the southern crossing into the small coastal territory on Sunday after rockets fired by Hamas's armed wing killed four Israeli soldiers there. The Israeli military then urged residents of the eastern districts of Rafah to evacuate, before taking control of the Palestinian side of the Rafah crossing with Egypt and closing it too. While Israel said it reopened Kerem Shalom on Wednesday, De Domenico said aid deliveries remain "extremely difficult". The Rafah crossing, through which all fuel destined for Gaza passes, remains closed. However, "there are no fuel reserves in Gaza". This means "there is no movement" and "this completely paralyses humanitarian operations", De Domenico said. The appeal comes as the international community calls for more aid to reach Gaza, where seven months of conflict have caused a severe humanitarian crisis. Even before the Rafah crossing was closed, the UN had been looking for alternative ways to get fuel into the territory for weeks, amid deep concern over Israel's threat of a large-scale ground operation in the city of 1.4 million people, De Domenico said. Israel has assured the UN it is trying to find a solution, De Domenico said, though he was sceptical it could reach the 200,000 litres needed each day. The head of the World Health Organization, Tedros Adhanom Ghebreyesus, said Wednesday that hospitals in the southern Gaza Strip had only "three days of fuel left". Catherine Russell, director of the UN children's agency UNICEF, warned Thursday that if fuel was not allowed in "the consequences would be felt almost immediately". The Hamas-run government in Gaza meanwhile said Thursday that in the past two days Israel had blocked the entry of more than 400 trucks carrying humanitarian aid and 160 cancer patients, and the exit of 160 wounded and sick people seeking medical treatment. Britain, meanwhile, completed its 11th airlift of aid to Gaza on Thursday, bringing the total to 110 tonnes, the British defence ministry said in a statement. The UK has delivered ready-to-eat meals, water, rice, tinned food and flour on 11 Royal Air Force (RAF) flights and 120 parachute drops, including 12 tonnes delivered to northern Gaza on Thursday alone. The aid is dropped along the northern coast of Gaza and British personnel work closely with the Jordanian air force to plan and execute each mission, the statement said. The US Department of Defense said Thursday it was still waiting for weather conditions in the Mediterranean to improve so it can deploy a temporary port built to boost aid deliveries to Gaza, which was completed this week. The project consists of two piers: a floating one where ships carrying aid will dock, and a causeway called the "Trident" along which trucks will drive to take the aid ashore. Read Also: After 21 deaths, Hamas asks for airdrops of aid to stop (Portuguese version)