United Nations humanitarian chief Valerie Amos has said aid must reach Typhoon Haiyan survivors more quickly.
Ms Amos spoke out amid reports of widespread hunger and thirst and as a mayor of one of the affected areas said he would not be able to maintain law and order unless food arrived soon.
Officials are preparing to bury some of the storm's thousands of victims in mass graves in the hope of minimising the spread of disease in typhoon-hit towns.
Meanwhile Philippine Energy Secretary Jericho Petilla has warned that it could take six weeks to restore power to some areas.
Ms Amos told reporters in Manila: "The situation is dismal. Those who have been able to leave have done so. Many more are trying. People are extremely desperate for help.
Officials are struggling to cope with the sheer scale of the disaster "We need to get assistance to them now. They are already saying it has taken too long to arrive. Ensuring a faster delivery is our ... immediate priority."
Criticism has been growing that help is taking too long to arrive in areas devastated by Typhoon Haiyan, known locally as Yolanda, last Friday.
Thousands of desperate survivors are clamouring to escape Tacloban, where clean drinking water is in short supply and scores of dead bodies lie piled up in bags outside the ruined city hall.
"There are still so many cadavers in so many areas. It's scary," the city's mayor Alfred Romualdez said, adding that retrieval teams were struggling to cope.
Body bags are piling up as preparations are made for mass burials He said: "There would be a request from one community to collect five or 10 bodies and when we get there, there are 40.
"We need more manpower and more equipment.
"I cannot use a truck to collect cadavers in the morning and then use it to distribute relief goods in the afternoon."
Mr Romualdez said the plan was to start mass burials in the nearby village of Basper on Thursday, after attempts to lay to rest some of Haiyan's victims were abandoned when gunshots halted a convoy travelling towards a communal grave.
City officials estimate that they have collected 2,000 bodies but insist many more need to be retrieved.
People queue to charge their mobile phones in Tacloban city The UN fears that 10,000 people may have died in Tacloban city alone, but President Benigno Aquino has described that figure as "too much".
US officials said relief was starting to get through, as an aircraft carrier expected to arrive in the Philippines by Friday headed towards the region.
Sky News Correspondent Katie Stallard, watching supplies arrive at an airfield in Cebu City, said: "We are seeing signs that the international relief effort is getting going, but many people will simply not know it is coming."
In Tabontabon, the town's mayor Brendo Gamez told Sky's Asia Correspondent Mark Stone that he feared a breakdown of law and order if aid was delayed.
He said: "We have no food ... if the people of Tabontabon suffer hunger, I don't think I can control them any more."
Some £13m has been raised by the British public in just 24 hours for emergency aid, which will go directly to help more than 11 million people affected by Typhoon Haiyan.

The Disasters Emergency Committee (DEC), a group of 14 UK aid organisations, said that while life-saving aid is on the move, agencies are battling to overcome blocked roads, closed ports, an ill-equipped airport and increasing security concerns.
The disaster-ravaged country has become "increasingly volatile" as people become desperate for food and water, with some resorting to force, the DEC said.
Coree Steadmen, Christian Aid's emergency manager in the Philippines, said: "The devastation here is unimaginable. Aid workers are walking for hours and not seeing a single standing building.
"Most roads are covered with fallen trees and collapsed houses. Where roads are accessible, they are gridlocked with cars fleeing the area.
"Getting aid through is tough, but we are resourceful and we will find a way."
:: To make a donation to the DEC Philippines Crisis Appeal visit www.dec.org.uk, call the 24-hour hotline on 0370 60 60 900, donate over the counter at any high street bank or post office or send a cheque.
You can also donate £5 by texting the word SUPPORT to 70000.
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