Relief agencies in Haiti are struggling to distribute aid in the city of Gonaives after tropical storm Jeanne caused floods and landslides there.
Only a handful of bodies have been identified
Crowds of hungry and thirsty people who may not have had food for days have been gathering around relief centres, hampering the handing out of supplies.
The authorities have continued to bury victims of the floods in mass graves.
At least 1,000 people are dead and with hundreds more missing, officials warn the final toll could be twice as high.
At one warehouse, there were angry scenes as several hundred people surged against the gates of the building desperate to get inside, reports the BBC's Dan Griffiths in Gonaives, Haiti's third largest city.
United Nations peacekeepers who have been deployed to assist the interim government are playing a crucial role in making sure rising tensions do not turn into outright violence, our correspondent says.
On the streets, floodwaters are gradually receding but many homes have been ripped apart, forcing the owners to live on the streets or on the rooftops of houses that are still intact.
The roads are covered in a thick coat of mud and there is a stench of raw sewage in the air.
Survivors have to drink and cook with water from ditches containing rotting bodies and sewage.
"It's a critical situation in terms of epidemics, because of the bodies still in the streets, because people are drinking dirty water and scores are getting injuries from
debris - huge cuts that are getting infected," Francoise Gruloos, Haiti director for the UN Children's Fund was quoted as saying by the Associated Press news agency.
Corpses have been dumped in a pit near Gonaives in an attempt to prevent the spread of disease, while unclaimed bodies continue to litter the city.
Dr Carl Murat Cantave, a government official, said truckloads of bodies had been delivered for burial at the Bois Marchand cemetery near Gonaives, Reuters news agency reported.
Bystanders reportedly shrieked and held their noses against the stench as the corpses were dumped into a four-metre (14ft) deep hole.
Only a couple of dozen bodies have been identified and more than 1,000 people are still missing.
"We're demanding they come and take the bodies from our fields," local resident Jean Lebrun told AP. "Dogs are eating them."
The confirmed death toll has reached 1,013 in Gonaives, with about 1,200 more missing.
The UN World Food Programme (WFP) estimates 175,000 people are without food, water and electricity.
UN helicopters have already taken emergency supplies to Gonaives.
Appealing for international support, UN Secretary General Kofi Annan said he was "deeply saddened by the heavy loss of life and destruction".
UN peacekeeping troops - sent to restore order after President Jean-Bertrand Aristide was overthrown in February - are working with aid agencies to help the victims.
Mr Aristide, in exile in South Africa, sent his "condolences and courage to an entire nation that has seen much pain and suffering".
Haiti is chronically vulnerable to flooding and mudslides because of widespread deforestation.
"When you remove vegetation, the topsoil washes away," an aid worker told AP.
In the neighbouring Dominican Republic - which has retained much of its forest cover - the death toll from Jeanne was 19.
NORTHERN HAITI UNDER WATER
Gonaives, the worst-affected city, is still largely under water.
In Port-de-Paix and Northwest province, at least 70 are reported dead. The city is described as under a dense crust of mud.
Bodies swept out to sea have washed up on La Tortue island, though aid agencies say the island itself was not hit as badly as at first thought.