U.N. Emergency Relief Coordinator Valerie Amos made the appeal Tuesday after arriving in Manila to coordinate relief efforts and survey the damage from Typhoon Haiyan, which ripped through nine regions in Southeast Asia over the weekend.
"Water supply and power are cut. Much of the food stocks and other goods are destroyed. Many health facilities are not functioning and medical supplies [are] quickly being exhausted," the U.N. humanitarian relief arm said in its latest action plan update.
U.N. officials say an estimated 11 million people were affected by one of the strongest storms to ever hit land. At least 670,000 people have been displaced.
Philippine officials said Typhoon Haiyan's official death toll of 1,774 only nips the surface, expressing fear the toll from the superstorm may hit 10,000.
Humanitarian workers have mounted "a massive humanitarian operation, battling heavy rains, blocked roads and damaged airstrips and seaports to reach millions across the region desperate for food, water and other basic necessities," the United Nations said in a statement.
U.N. and other relief agencies say transport logistics remains the biggest challenge, with large amount of debris blocking airports, roads and other access routes.
Adrian Edwards, spokesman for the U.N. Refugee Agency, said delays in providing humanitarian access is also "contributing to a breakdown in law and order as some desperate people loot shops for food and water."
There are unconfirmed reports of people destroying bank teller machines and robbing relief supplies, Edwards told reporters in Geneva, Switzerland.
"Women and children are begging on the streets for donations, exposing themselves to abuse and exploitation," he said.
As authorities worked to save survivors four days after Haiyan devastated a large swath of the Philippines, a tropical low blew in Tuesday delivering more rain, CNN reported.
Zoraida, named by the Philippine weather agency, is not a strong storm but has dumped just under 4 inches of rain in some places, meteorologists say.
The new storm is holding up needed aid in at least one province, Iloilo, where Gov. Arthur Defensor Sr. grounded relief flights until it has passed.
Zoraida also slowed air aid in the Cebu province, although military planes still made aid drops, an official said.
A 4.8-magnitude earthquake Tuesday also shook San Isidro, which is in the affected area, the U.S. Geological Survey reported.
Officials say it may take months to restore electricity throughout devastated areas. Entire houses, vehicles trees and other debris covered miles of roadways, making rescue, recovery and aid efforts difficult.
More than 2 million people need food aid, the Philippine government said.
Tomoo Hozumi, the Philippines' UNICEF representative, said food, shelter, clean water and sanitation were "in a severe shortage."
"The situation on the ground is very hideous," he told CNN.
Soldiers shot and killed two members of the militant New People's Army Tuesday when they ambushed a government aid convoy, the state-run Philippine News Agency reported.
Philippine Ambassador to the United States Jose Cuisia Jr. said the Philippines experiences about two dozen typhoons a year, but couldn't recall one worse than Haiyan.
"We have 20 to 24 a year. But we have not seen anything like this in the past," Cuisia told CNN.
Philippine President Benigno S. Aquino III declared a state of calamity in the stricken areas, giving the government expanded powers to deal with the crisis, including the fixing of the prices of goods.
Philippine officials have been answering criticism over the pace of relief efforts, The New York Times reported.
"There are lots of remote areas that haven't received aid," Aquino spokesman Ricky Carandang said. "The priority is to get food and water supplied. With communications partially functioning, with ports and roads blocked, we need to get that clear first. We need to get the roads clear before you can get the aid to them."
Aid pledges began pouring in Monday, including $25 million from the United Nations, $4 million from the European Union, $16 million from Britain and $10 million from the United Arab Emirates.
U.N. and U.S. civilian disaster assessment teams were on the scene. U.S. Marines based in Japan worked to outfit the shattered airport in hard-hit Tacloban with lights, radar and other gear to allow it to operate 24 hours a day, CNN said.
The United States and the United Kingdom have pledged to dispatch Navy vessels to the Philippines to assist in recovery efforts.
"There has been a lot of commentary that relief is not moving as fast as it should be," Praveen Agrawal, the World Food Program's Philippines representative and country director, told the Times. "The reality on the ground is there is such a level of devastation.
"Under normal circumstances, even in a typhoon, you'd have some local infrastructure up and some businesses with which you can contract," Agrawal said. "Being as strong as it was, it was very much like a tsunami. It wiped out everything. It's like starting from scratch."
After it devastated the Philippines, Typhoon Haiyan weakened as it emerged in the South China Sea but killed 14 more people in Vietnam and five more in China.