Cyrus Trimar lashed his three infants to a roof truss to stop them being washed away by the ocean as Super Typhoon Haiyan ripped through the Philippines.

Now he must scavenge for food to keep them alive, desperate for aid that sits undistributed in warehouses as lawlessness and shaky infrastructure hold up supplies desperately needed by the hungry and destitute survivors.

Trimar, who has picked up noodles from an overturned grocery van and butchered a stray pig, is one of thousands who took to helping himself because the outside assistance he had hoped for has not arrived.

"If only food aid arrived immediately, all this looting would have been avoided," he told AFP.

The plight of 29-year-old Trimar is far from unique amongst survivors of the category five storm which hit on Friday with winds reaching 315 kilometres (195 miles) an hour, generating waves up to five metres (16 feet) high that surged inland like a tsunami.

Almost a week after one of the strongest storms on record devastated large swathes of the Philippines' central islands, flattening homes and killing possibly thousands, the United Nations has admitted it had not been able to get help in quickly enough.

Even as the international community pledges tens of millions of dollars worth of help, aid agencies lament a shortage of trucks and fuel, bottlenecks on routes into the devastated city of Tacloban and security fears, with reports of aid convoys being ambushed.

"The looting and general insecurity has been a concern," said Cat Carter of Save the Children. "Finding a safe place to store aid overnight is a real challenge."

She added that her team could not "co-ordinate the relief effort properly" because of disrupted communications.

"Electricity being down is a huge problem because we don't have power for a lot of what we need to do. We need to bring generators in but you can't on these smaller planes," Carter said.

"The combination of challenges makes it extremely difficult to deliver the aid we need. It's incredibly frustrating."

Gwendolyn Pang, secretary general of the Philippine Red Cross, said the situation was really difficult.

"We need a sense of normalcy," she said, adding people should not have to see "dead bodies, dead animals and debris everywhere".

Tacloban mayor Alfred Romualdez echoed that sentiment, and said the number of dead and their presence all over the city was hampering the response.

"I cannot use a truck to collect cadavers in the morning and use it to distribute relief goods in the afternoon," he said.

We need "more manpower and more equipment. Let's get the bodies out of the streets. It's creating an atmosphere of fear and depression."

He said aid agencies were not moving in quickly enough because they wanted to know how much help was needed before they went into the town -- information, he said, that was not readily available.

"It's like a bank robbery -- it's better to have all units respond. We're on the seventh day already and they are still estimating. We need an overwhelming response," he said.

On Thursday UN humanitarian chief Valerie Amos said the scale of the disaster and the logistical challenges it posed meant some places still remained without help.

"There are still areas that we have not been able to get to where people are in desperate need," she told reporters in Manila "I very much hope that over the next 48 hours that that will change significantly."

"I do feel that we have let people down."