* Aquino under mounting pressure over aid distribution
* Relief efforts pick up with arrival of U.S. aircraft carrier
* "We are very, very worried about millions of children"-UNICEF
Survivors began rebuilding homes destroyed by one of the world's most powerful typhoons and emergency supplies flowed into ravaged Philippine islands, as the United Nations more than doubled its estimate of people made homeless to nearly two million.
But the aid effort was still so patchy that bodies lay uncollected as rescuers tried to evacuate stricken communities on Saturday, more than a week after Typhoon Haiyan killed thousands with tree-snapping winds and tsunami-like waves.
After long delays, hundreds of international aid workers set up makeshift hospitals and trucked in supplies, while helicopters from a U.S. aircraft carrier ferried medicine and water to remote, battered areas where some families have gone without food and clean water for days.
"We are very, very worried about millions of children," U.N. Children's Fund spokesman Marixie Mercado told reporters in Geneva.
A U.N. official said in a guarded compliment many countries had come forward to help.
"The response from the international community has not been overwhelming compared to the magnitude of the disaster, but it has been very generous so far," Jens Laerke of the Office for the Coordination of Humanitarian Affairs told the Geneva news briefing.
Captain Victoriano Sambale, a military doctor who for the past week has treated patients in a room strewn with dirt and debris in Tacloban, which bore the brunt of the storm, said there had been a change in the pace in the response.
"I can see the international support coming here," he said.
But he is still overwhelmed. "Day one we treated 600-plus patients. Day two we had 700-plus patients. Day three we lost our count."
President Benigno Aquino, caught off guard by the scale of the disaster, is scheduled to visit typhoon-affected areas on Saturday. He has been criticised for the slow pace of aid distribution and unclear estimates of casualties, especially in Tacloban, capital of hardest-hit Leyte province.
A notice board in Tacloban City Hall estimated the deaths at 4,000 on Friday, up from 2,000 a day before, in that town alone. Hours later, Tacloban mayor Alfred Romualdez apologised and said the toll was for the whole central Philippines.
The toll, written on a whiteboard, is compiled by officials who started burying bodies in a mass grave on Thursday.
Romualdez said some people may have been swept out to sea and their bodies lost after a tsunami-like wall of seawater slammed into coastal areas. One neighbourhood with a population of between 10,000 and 12,000 was now deserted, he said.
The City Hall toll was the first public acknowledgement that the number of fatalities would likely far exceed an estimate given this week by Aquino, who said lives lost would be closer to 2,000 or 2,500.
Official confirmed deaths nationwide rose by more than 1,200 to 3,621 on Friday. "I hope it will not rise anymore. I hope that is the final number," said Eduardo del Rosario, director of the National Disaster Risk Reduction and Management Council. "If it rises, it will probably be very slight."
U.S. HELICOPTERS AID RELIEF EFFORT
But massive logistical problems remain. Injured survivors waited in long lines under searing sun for treatment. Local authorities reported shortages of body bags, gasoline and staff to collect the dead.
"Bodies are still lying on the roads. But now at least they're in sections with Department of Health body-bags," Ian Norton, chief of a team of Australian aid workers, told Reuters.
The number of people made homeless by the storm rose to 1.9 million, up from 900,000, the U.N.'s humanitarian agency said. In Tacloban alone, at least 56,000 people face unsanitary conditions, according to the U.N.'s migration agency.
Stunned survivors in Tacloban said the toll could be many thousands.
"There are a lot of dead people on the street in our neighbourhood, by the trash," said Aiza Umpacan, a 27-year-old resident of San Jose, one of the worst-hit neighbourhoods.
"There are still a lot of streets that were not visited by the disaster-relief operations. They are just going through the highways, not the inner streets," he said. "The smell is getting worse, and we actually have neighbours who have been brought to hospital because they are getting sick."
Across the city, survivors have begun to rebuild. The sounds of hammers ring out. Men gather in groups to fix motorbikes or drag debris off splintered homes and wrecked streets. Most have given up searching for lost loved ones.
The preliminary number of missing as of Friday, according to the Red Cross, rose to 25,000 from 22,000 a day earlier. That could include people who have since been located, it said.
The nuclear-powered USS George Washington aircraft carrier and accompanying ships arrived off eastern Samar province on Thursday evening, carrying 5,000 crew and more than 80 aircraft.
U.S. sailors have brought food and water ashore in Tacloban and the town of Guiuan, whose airport was a U.S. naval air base in World War Two. The carrier is moored near where U.S. General Douglas MacArthur's force landed on Oct. 20, 1944, in one of the biggest Allied victories.
Acting U.S. Ambassador Brian Goldbeck, the chargé d'affaires at the U.S. Embassy in Manila, said the United States had moved 174,000 kg (383,000 lb) of emergency supplies into affected areas and evacuated nearly 3,000 people.