* International aid getting through slowly
* Frustrated survivors block roads with corpses
* Troops, doctors, planes full of food head for Haiti
(Adds details, Cuba to let U.S quake relief flights through airspace)
By Catherine Bremer and Andrew Cawthorne
PORT-AU-PRINCE, Jan 15 (Reuters) - Thousands of people left hurt or homeless in Haiti's earthquake spent a third night lying on sidewalks and clamored for help on Friday as their despair turned to anger and aftershocks rippled through the wrecked city.
Governments across the world are pouring relief supplies and medical teams into the quake-hit Caribbean state -- already the poorest in the Western Hemisphere. But huge logistical hurdles and the sheer scale of the destruction mean aid is still not reaching hundreds of thousands of hurt and homeless people in the devastated coastal capital Port-au-Prince.
"These people have lost everything, They have nothing. They have been waiting for two days now. No one is helping us. Please bring us water or people will die soon," said Renelde Lamarque, who has opened his home yard to about 500 quake victims in the devastated Fort National neighborhood.
Raggedly dressed survivors held out their arms to a reporter, begging for food and water.
Tens of thousands are feared dead from Tuesday's quake and dangerous aftershocks still ripple every few hours through the city, dislodging debris and increasing the anguish of people already traumatized by death and injury on a massive scale.
A big aftershock jolted buildings at about 5 a.m (1000 GMT) on Friday, causing fresh alarm.
Relief workers said some aid was trickling through to people but in haphazard fashion, and they said coordination was desperately needed. "Some aid is slowly getting through, but not to many people," said Margaret Aguirre, a senior official with International Medical Corps.
But as the risk of starvation and disease increased in shattered streets strewn with rubble, garbage and rotting bodies, most Haitians said they had still received nothing.
"I haven't eaten since the day before yesterday, we've lost our house, we've nothing to eat, nobody has come, we've seen nobody, not even a minister or a senator," said Bertilie Francis, 43, who was with her three children.
"We are here by the Grace of God, nobody else," she said.
In one part of Port-au-Prince on Thursday, desperate Haitians blocked streets with corpses in a protest to demand quicker relief efforts, witnesses said.
Aguirre said aid agencies were discussing setting up a central refugee camp to try to group a multitude of victims' settlements springing up all over Port-au Prince.
"The key is the coordination. So many relief workers are just out of the picture. We want to avoid people just running round doing their own thing," she said.
PRAYERS, GROANS AND WAILS
In a sign that international relief efforts cut across ideological differences, communist-led Cuba agreed to let the U.S. military use restricted Cuban air space for medical evacuation flights carrying Haitian earthquake victims, sharply reducing the flight time to Miami, a U.S. official said.
United Nations disaster experts said at least 10 percent of housing in the Haitian capital was destroyed, making about 300,000 homeless, but in some areas 50 percent of buildings were destroyed or badly damaged.
U.N. aid agencies were to launch an emergency appeal for approximately $550 million on Friday to help survivors.
The U.N. peacekeeping mission in Haiti, which has lost at least 36 of its personnel in the quake, was trying to provide some basic coordination from an office near the airport.
In the capital overnight, an eerie chorus of hymns, prayers, groans and wails of mourning, mixed with the barking of terrified dogs, echoed over the hilly neighborhoods.
Bodies lay all around the hilly city, and people covered their noses with cloth to block the stench of death. Corpses were piled on pickup trucks and delivered to the General Hospital in Port-au-Prince, where hospital director Guy LaRoche estimated the bodies piled outside the morgue numbered 1,500.
Three days after disaster struck, masses of people clamored for food and water, as well as help in digging out relatives still missing under the rubble.
Angry survivors built the roadblocks with corpses as aid committed from 30 countries began arriving in Port-au-Prince in dozens of planes that clogged the city's small airport.
Shaul Schwarz, a photographer for TIME magazine, 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. People are fed up with getting no help," he told Reuters.
The presidential palace, the parliament, the cathedral and many government buildings collapsed. The main prison also fell, allowing dangerous criminals to escape.
U.S. forces were trying to step up operations at the airport in order to get more supplies into the country.
The Haitian Red Cross said it believed 45,000 to 50,000 people had died and 3 million more -- one third of Haiti's population -- were hurt or left homeless by the major 7.0 magnitude quake that hit its impoverished capital on Tuesday.
"We have already buried 7,000 in a mass grave," President Rene Preval said.
The Haitian Red Cross said it had run out of body bags.
Doctors in Haiti were ill-equipped to treat the injured. Relief workers warned that many more people will die if the injured, many with broken bones and serious loss of blood, do not get first aid in the next day or so.
Planes full of supplies and search and rescue equipment began to arrive at Port-au-Prince airport on Thursday faster than ground crews could unload them, jamming the limited ramp space and forcing arriving aircraft to circle for up to two hours before landing.
U.S. President Barack Obama pledged an initial $100 million for Haiti quake relief and enlisted former U.S. presidents Bill Clinton and George W. Bush to help raise more, vowing to the Haitian people: "You will not be forsaken."
The United States was sending 3,500 soldiers, 300 medical personnel, several ships and 2,200 Marines to Haiti.
The U.S. Navy said its nuclear-powered aircraft carrier USS Carl Vinson will arrive on Friday to serve as a "floating airport" for relief operations by its 19 helicopters.
Nations around the world pitched in to send rescue teams with search dogs and heavy equipment, helicopters, tents, water purification units, food, doctors and telecoms teams. But aid distribution was hampered because roads were blocked by rubble and smashed cars and normal communications were cut off. (Additional reporting by Tom Brown, Kena Betancur and Carlos Barria in Port-au-Prince, Stephanie Nebehay in Geneva and Steve Holland in Washington; writing by Anthony Boadle and Pascal Fletcher; editing by Vicki Allen and Eric Beech)
- Reuters - Thomson Reuters Foundation
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