Harrowing images from the Haitian capital Port-au-Prince on Thursday showed the horror facing rescue workers as recovered dead bodies littered the streets.

In scenes reminiscent of a horror film, uncounted bodies were lined up across pavements, many only partially covered with white cloth in the 80-degree (27 degree Celsius) heat, as dust-caked arms and legs reached, frozen and lifeless, from the ruins.

On Thursday, some people tried to drag the dust-covered dead along roads toward the morgue, where people came to search for relatives.

Others bodies were piled into earth moving machines and loaded into trucks.

Emotional local residents were working tirelessly to clear the streets but said they desperately needed support.

"Now we do our best but what we can do?" one resident said.

Photographs from outside the General Hospital morgue, showed hundreds of collected corpses covering the parking lot, as grief-stricken relatives searched for loved ones.

Brazilian UN peacekeepers, key to city security, have been trying to organise mass burials.

There have been reports that some resident tried to carry dead relatives to nearby hills for impromptu burials, prompting Brazil's military - the biggest continent among United Nations peacekeepers - to warn that the practice could lead to an epidemic, and have asked authorities to create a new cemetery.

The International Red Cross has estimated that 45-thousand to 50-thousand people were killed in Tuesday's magnitude-7.0 quake, based on information from the Haitian Red Cross and government officials.

However, there are easily hundreds, and perhaps thousands, of people still trapped, living or dead, in collapsed buildings.

Some 40 search-and-rescue teams from around the world were on the ground in Haiti on Thursday, looking for survivors trapped inside collapsed buildings.

But to find and save people, the rescuers need heavy machinery to lift tons of rubble - equipment that teams from places like Britain and Iceland have, but others don't.

In the meantime, friends and relatives who survived the quake have been clawing at the wreckage, often with bare hands, in an effort to find missing loved ones.

Relief supplies and emergency experts did start to pour into Haiti from around the world on Thursday, but aid groups said the challenge of helping Haiti's desperate quake survivors was enormous.

Aid deliveries by ship were impossible to Port-au-Prince because the Haitian capital's port was closed due to severe damage from Tuesday's quake.

The city's airport was open but damaged, labouring mightily to handle a flurry of incoming aid flights.