Seven-year-old Stepanie lies injures in a makeshift hospital on a street in Port-au-Prince January 15, 2010. [Xinhua]

The United Nations and its partners Friday appealed for 562 million U.S. dollars to help the victims of the devastating earthquake that jolted Haiti earlier this week, as the world body scales up its assistance in the wake of the disaster.

The 7.0-magnitude tremor which struck the Western Hemisphere's poorest country on Tuesday is estimated to have affected one third of the nation's 9 million people.

The earthquake has devastated the capital, Port-au-Prince, leaving basic services on the brink of collapse. The UN estimates that 10 percent of the buildings in the city have been destroyed, leaving 300,000 people homeless, and many are fleeing the destruction.

The 562 million U.S. dollars is intended to assist an estimated 3 million affected people over a period of six months, with half of the funds being earmarked for emergency food aid, with the rest targeted at health, water, sanitation, nutrition, early recovery, emergency education and other key needs. The UN Central Emergency Response Fund (CERF) has allocated 25 million U.S. dollars towards the appeal.

Because of the lack of detailed information from the ground, the appeal will be revised in the coming weeks, Under-Secretary-General for Humanitarian Affairs John Holmes told reporters at the UN headquarters in New York.

A resident carries Samael Jachond, who was rescued from the remains of his house, four days after a major earthquake hit the capital Port-au-Prince January 15, 2010. [Xinhua]

The UN is working to overcome serious obstacles to providing aid posed by lack of infrastructure and other issues, and Holmes underscored the need to recognize the reality that "inevitably and despite everyone's enormous efforts," it will take some time to scale up the pace of the operations.

With the top UN official in Haiti, Hedi Annabi, still unaccounted for, Secretary-General Ban Ki-moon dispatched Edmond Mulet, his former Special Representative to Haiti and current Assistant-Secretary-General for Peacekeeping Operations, to the country to assume full command of the UN Stabilization Mission in Haiti (MINUSTAH) and coordinate the relief effort.

The Office for the Coordination Affairs (OCHA) said that food and medical help have started to arrive in Port-au-Prince, but on a limited scale.

OCHA is coordinating some 27 search-and-rescue teams -- considered a top priority as many people remained trapped under rubble -- while a further 10 teams are set to arrive shortly.

Dozens of nations have offered their assistance, and the UN is working to ensure that the aid reaches people as quickly as possible.

With many survivors having sustained serious injuries, including traumatic wounds and crushed limbs, medical support has been identified as an immediate need, along with food, water and shelter. The UN World Health Organization (WHO) is coordinating medical assistance and sending a 12-member team specializing in victim care, while its partners are ramping up their efforts on the ground.

Rescuers provide medical aid to an earthquake victim named Perst, 35, in the capital Port-au-Prince January 15, 2010. [Xinhua]

The WHO said Thursday that eight hospitals were damaged or destroyed in Haiti and two damaged in neighboring Dominican Republic. "We fear that the impact of this earthquake will be particularly devastating to the already existing vulnerability of Haiti's people, society and economy," said WHO's Paul Garwood.

OCHA said Friday that while the number of mobile hospitals set to arrive in the country is sufficient, there is still a great need for doctors, nurses and medicine. The Office also noted that it is conferring with Haitian authorities on the possibility of the national soccer stadium being used as a field hospital location.

For its part, the World Food Program (WFP) is continuing with its food distributions, aiming to reach 2 million people affected by the quake.

The agency refuted media reports that its warehouses in Haiti had been looted and its food stocks stolen. It is also acquiring two helicopters that it will send to the country immediately, and moving nearly 90 metric tons of high-energy biscuits from El Salvador.

Meanwhile, the UN Children's Fund (UNICEF) highlighted as one of its key concerns identifying and reuniting children who have been separated from their parents in the disaster, as well as finding the extended families of orphaned children.

Nearly half of Haiti's population is under the age of 18, making children very vulnerable, UNICEF stressed, adding that many children are on the streets of Port-au-Prince, hungry, thirsty and traumatized.

It is working around the clock to register children who are on their own, as well as to provide water purification tablets, latrines, shelter materials and hygiene kits.