ISLAMABAD (Agencies) - Pakistan is facing one of the worlds worst displacement crises, with aid workers struggling to reach many of the two million people who have fled fighting, a top UN official said Tuesday. Rashid Khalikov, director of the UN humanitarian office in New York, appealed for more funds to help the massive numbers crammed into dusty camps or in relatives homes, seeking refuge from an anti-Taliban assault. I would say that it is one of the worst displacement crises, said Khalikov, who is currently visiting Pakistan. We have this massive number of people that got displaced and the absolutely horrible speed with which this happened. They got displaced into a hostile climate zone, they are not used to living in these kind of temperatures. The UN refugee agency said late Monday that 1.45 million people have fled and registered with authorities since May 2, joining more than 550,000 people displaced by similar battles last year. I think we are still trying to catch up with this increasing number of people, said Khalikov. Relief efforts were certainly not sufficient because we are still not reaching those who are in need, he said. Only 15 percent of the freshly displaced are sheltering in official camps, he said. The rest are staying with families, creating logistical hurdles in the delivery of aid to a scattered community. In some instances the population of villages and towns doubled... These communities, they are not very rich so they cannot offer a lot, he said. Medical issues were also a key concern, Khalikov told AFP. The hygienic and sanitary conditions are not up to standard, he said. It is very hot and the vulnerability in terms of health increases dramatically in these kinds of conditions. Authorities has said Lower Dir and Buner are back under government control and urged people to return, but Khalikov said the UN had not seen any large movement of people and expected the crisis to drag on. We are trying to ensure that the decision on their return they will take voluntarily, and they will return to a secure environment, and will return in dignity and will not be coerced, he said. The United Nations plans to launch an appeal for funds to help the displaced later this week. The number of people displaced by fighting between security forces and the Taliban reached two million as the UN warns the conflict is turning into the largest displacement crisis since the Rwandan genocide. Were talking about 1.5 million people displaced in two weeks and over 2 million in less than a year... its the fastest and most massive movement of people since Rwanda.