People have started blocking roads with corpses in Haiti's capital Port-au-Prince to protest against the delay in emergency aid, an eyewitness says.

TIME magazine photographer Shaul Schwarz said he saw at least two downtown roadblocks formed with bodies of earthquake victims and rocks.

"They are starting to block the roads with bodies; it's getting ugly out there," he said. "People are fed up with getting no help."

Aid has not yet reached the shell-shocked residents of Port-au-Prince, who are wandering their broken streets searching for water, food and medical help as night falls for the third time since the earthquake.

The stench of death from decomposing bodies hung over Port-au-Prince as residents prepared for another night in the open.

Estimated death toll 50,000

Estimated death toll 50,000 7,000 victims buried in mass grave

7,000 victims buried in mass grave Up to 3 million injured or homeless

Up to 3 million injured or homeless Car parks full of bodies

Car parks full of bodies Aid and rescue teams backed up at airport

Aid agencies say the quake-hit nation desperately needs supplies and security or the situation there could turn violent, putting up to 3 million vulnerable people at further risk.

Foreign rescue teams are yet to be fully deployed in the capital, 48 hours after the earthquake struck, and have been told they will not be able to start their searches until the morning, local time.

ABC correspondent Craig McMurtrie spoke to Greg Barhost from South Florida Urban Search and Rescue at Port-au-Prince airport shortly before nightfall.

"We have been told there is much destruction and also that it's very unsafe at night," Mr Barhost said.

He said his rescue team would not be able to start its searches until the morning.

A local US security expert, Blair Hawkins, says people in the city are running out of patience. "The people are getting angry. There's no water, there's no food out there," he told the ABC.

Officials say the full search and rescue effort will resume tomorrow.

The US is sending more than 5,000 soldiers and marines to Haiti as well as 300 medical personnel and an aircraft carrier which will act as a floating airport to ferry aid into the devastated capital.

Matt Marek from the American Red Cross says without the presence of troops, the situation could deteriorate quickly as desperate people fight for supplies.

"We're going to need assistance, certainly from the US Government, to really control things down here, because I think as the days get on there's a risk of escalation ... perhaps trouble," he said.

"We're going to be able to help people less if the security situation worsens."

One foreign aid worker said money was worthless and water had become the currency on the streets of Port-au-Prince.

Looters have swarmed a broken supermarket in Port-au-Prince, carrying out electronics and bags of rice, while others siphoned petrol from a wrecked tanker.

"All the policemen are busy rescuing and burying their own families," said tile factory owner Manuel Deheusch.

"They don't have the time to patrol the streets."

"My family's dead. I had one brother. He's dead," one survivor said. "I don't have anyone, or any money. I don't have a house. I don't know what I'm going to do now."

Victims buried in mass graves

The Red Cross estimates the death toll from the earthquake is likely to be at least 50,000, with another 3 million people injured or homeless.

About 7,000 victims killed in the quake have already been buried, Haitian President Rene Preval said this morning.

"We have already buried 7,000 in a mass grave," Mr Preval told reporters at the airport while accompanying Dominican Republic President Leonel Fernandez, the first foreign head of state to visit Haiti after the quake.

Mr Fernandez said one of the most important things Haiti needed was help in burying its dead.

The director of the general hospital in Haiti's capital, Port-au-Prince, says at least 1,500 bodies are stacked inside and outside its morgue and trucks are continuing to deliver more.

Search and rescue teams are slowly moving through Port-au-Prince, seeking signs of life with cameras and listening devices.

Not far from the national palace, a group of men used their bare hands to rescue a 15-year-old girl from a building. Only her feet were visible.

She heard other people dying around her and four of her relatives did not make it out.

Aid efforts paralysed

International relief to Haiti was reduced to a trickle this morning after the capital's airport was overwhelmed by a sudden influx of aid planes, which created a dangerous bottleneck.

US aviation authorities say Haiti has asked countries not to authorise any more flights to Port-au-Prince for now.

The USS Carl Vincent, an aircraft carrier which has space for 19 helicopters, should arrive off the coast of Haiti tomorrow, where it will serve as a floating airport.

Aid deliveries by ship are impossible because the port in the capital has been badly damaged.

Mr Marek from the Red Cross says the trickle of aid must turn into a flood.

"There's a need for food, there's a need for water; we have to start thinking short term and long term, we've got to start thinking camp management," he said.

"We've got a lot of hygiene and sanitation needs that are going to be coming up very quickly."

- ABC/agencies