The United Nations country coordinator Soe Nyunt-U appealed foreign governments and aid agencies for financial support to provide clean water, food and emergency shelter to about half a million people affected by the disaster.

The UN "calls for US$28.6 million to support the... Philippines to respond to the serious humanitarian needs caused by the devastating storm", Soe said in a statement.

"It was as if the cities were hit by an inland tsunami," he said, recounting the horror and devastation of the flash floods unleashed by tropical storm Washi on the southern ports of Iligan and Cagayan de Oro.

"Entire areas were completely flattened; only a few sturdy buildings remain standing, and these sustained a lot of damage," he said.

Soe, who recently visited the disaster area, added that clearing debris was also a priority to reduce health risks to about 471,000 of the worst-affected people.

Soe said the disaster left 1,060 people dead or missing and damaged or destroyed more than 28,000 homes.

The official death toll from the weekend disaster, which swept away shanty towns built near major rivers, has exceeded 1,000 but some authorities said hundreds more people could be missing and may never be found.

Benito Ramos, the civil defence chief, told AFP that eight navy and coastguard ships had been drafted in to find corpses floating among debris up to 100 kilometres (62 miles) offshore.

"By this time, there will be no survivors, just dead bodies," he said after tropical storm Washi brought heavy rains before dawn on Saturday that spawned flash floods, overflowing rivers and mudslides.

Rolando Balili clutched on to driftwood for more than 24 hours after he, his wife, six other family members and their neighbours were swept 35 kilometres out to sea.

"I heard voices in the sea of so many people crying for help, but there was nothing I could do except cling to my log," said the 29-year-old, whose arm and leg were both fractured by debris.

He and his wife were rescued by fishermen on Sunday, but the bodies of his two sisters and two-year-old daughter were among those retrieved from the waters, while his five-year-old son and both parents remain missing.

Bruised, sun-burnt and in crutches, Balili -- who washes cars for a living -- spoke to AFP on Thursday while standing in long queue seeking assistance from the civil defence office in Cagayan de Oro city.

Ramos put the death toll at 1,010 while his agency, the National Disaster Risk Reduction and Management Council, put the number of missing at 51.

But Lawrence Cruz, mayor of the hard-hit port of Iligan, said that in his city alone 283 people had been confirmed dead while more than 400 had been reported missing.

"We could only assume they are dead already," he said. "There is so much mud that has to be cleared up and maybe the missing are buried."

Philippine Red Cross chief Gwendolyn Pang said that at least 900 bodies had been recovered and that some 400 people have been reported missing.

However, she said the exact toll may never be known as some of those reported missing may be among the dead, and there could be many more whose disappearances were never reported.

"Many will never be found and we don't know how many are really missing. No one will report them because entire families were swept away," Pang added.

Iligan and the larger nearby port of Cagayan de Oro accounted for most of the confirmed deaths so far.

A navy vessel recovered 11 badly decomposed bodies off the coastal town of Salay on Wednesday, navy spokesman Lieutenant-Colonel Omar Tonsay told AFP.

"You have to ram logs and risk holing your hull or entangling your propellers," Tonsay said, describing the dangers search and rescue teams face from floating debris themselves.

Ramos said the maritime search could continue for two more weeks, but warned that many bodies may have sunk underwater and would never be found.

The main priority was finding permanent shelter for the 309,000 people displaced by the floods, particularly more than 43,000 housed in cramped evacuation centres, he said.

Health officials have warned of the risk of epidemics breaking out at the camps, which remain without proper water supply and sanitation.

Many of those in the evacuation centres are forbidden from returning home as the flood-prone areas have been identified by government as too dangerous for human habitation.