|Haiti's president says 7,000 people have already been laid to rest in a mass grave [EPA]
Rescue teams and emergency supplies are slowly getting on the ground in Haiti as the Caribbean nation begins burying thousands killed in Tuesday's devastating earthquake.
Nations around the world pledged millions in aid and sent rescue teams, doctors and relief supplies.
But the influx of aid had yet to reach most survivors in the capital Port-au-Prince on Thursday, with distribution hampered by blocked roads, severed communications lines and relief agencies' offices dealing with damaged offices and missing staff.
The capital's port was too badly damaged to handle cargo and supply planes arrived at the airport faster than ground crews could unload them, prompting aviation authorities to restrict non-military flights from US airspace for fear planes would run out of fuel while waiting to land.
Alejandro Lopez-Chicheri, the senior spokesman for the World Food Programme for Latin America, Central America and the Caribbean, said that Haiti was "completely on the ground".
"The roads, many of them are still to be opened, and on the ones that are open there are still people concentrated on the sides of the roads," he told Al Jazeera from Port-au-Prince.
"This is a logistical challenge. Before the earthquake struck we were already assisting one million people here, we are considering it will be at least double that after this earthquake."
Rescue crews from the Dominican Republic, Venezuela, the United States, France and Bolivia were among the first to arrive on Thursday to help Haitians dig their friends and relatives out of the rubble.
But thousands of people were believed to still be trapped more than 48 hours after the quake and in many areas Haitians were digging with their bare hands in an attempt to find the missing.
Ansel Haerz, a journalist in Port-au-Prince, told Al Jazeera that in the absence of international rescue workers, local people were working together, often with little more than their hands, to dig through the debris for survivors.
Al Jazeera's Mike Kirsch reports on Haiti quake survivors who have been left homeless
"Haitians are coming together, I have seen them many times, crowded around a little spot in a building where there is a little space trying to hear if anyone is trapped beneath it and trying to get people out," he said.
Even if people were pulled out from under the debris, however, many hospitals were too battered to use, and doctors struggled to treat crushed limbs, head wounds and broken bones at makeshift facilities where medical supplies were scarce.
Rene Preval, the Haitian president, said 7,000 people had already been buried in a mass grave.
And the Haitian Red Cross said it believed 45,000 to 50,000 people had died and three million more - one third of Haiti's population - had been hurt or left homeless by the 7.0 magnitude quake that struck the impoverished nation on Tuesday.
Bodies lay all around the hilly city and people covered their noses with cloth to try to block the stench. The Red Cross said it had run out of body bags.
"There is a condition of total misery in downtown Port-au-Prince at this late hour," Al Jazeera's Mike Mirsch, reporting from Port-au-Prince, said.
"We have seen bodies that have been there since the first day the quake hit. It is the second day now, going into the third day and the bodies have not been collected.
"The stench of death is very strong in Port-au-Prince."
UN peacekeepers, who lost at least 36 of their own in the quake, seemed overwhelmed by the enormity of the rescue effort.
"We just don't know what to do," a Chilean peacekeeper said. "You can see how terrible the damage is. We have not been able to get into all the areas."
Jamieson Davies, the international programmes director for the Caritas relief organisation, said that the situation was "extremely difficult" as aid workers were suffering the same hardships as the Port-au-Prince residents.
"Even the aid workers themselves are sleeping in cars or in tents on the streets," she told Al Jazeera from Sydney, Australia.
"But luckily they have direct access to stocks of relief that were already placed around the country.
"Right now our staff are delivering first aid to survivors, as well as blankets, tents, things that they need to spend the night safely on the streets."
Many people were gathered in parks, either sleeping on the ground or under makeshift tents as they waited for aid to arrive.
Sobs and wailing could be heard each time another person died, but aftershocks interrupted the mourning, sending people scrambling.
Al Jazeera's Kirsch said he could hear many groups of survivors singing and praying in the dark, thanking God for giving them another day.
"Water has started to flow from some of the government trucks we have seen and that has certainly brightened the spirits," he said.
"There is a sense of solidarity and unity on the streets, just by the misery they are sharing."
In the US, Barack Obama pledged $100m in aid to Haiti and said the US would grant "every element of our national capacity, our diplomacy and development assistance, the power of our military and most importantly, the compassion of our country" to Haiti.
"To the people of Haiti, we say clearly and with conviction, you will not be forsaken, you will not be forgotten," said the US president, who has ordered 6,000 troops, including 300 medical personnel, to Haiti.
Source: Al Jazeera and agencies