* Aquino under mounting pressure over aid distribution
* Relief efforts pick up with U.S. aircraft carrier
* "We are very, very worried about millions of children"-UNICEF (Adds comments from residents, details from Ormoc city, US military aid)
By Aubrey Belford
TACLOBAN, Philippines, Nov 16 (Reuters) - 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 patchy, and bodies still lay uncollected as rescuers tried to evacuate stricken communities on Saturday, more than a week after Typhoon Haiyan killed at least 3,633 with tree-snapping winds and tsunami-like waves.
"We are very, very worried about millions of children," U.N. Children's Fund spokesman Marixie Mercado told reporters in Geneva. There are officially 1,179 people missing, according to the national count.
Survivors and officials in Tacloban, which bore the brunt of the storm, have said the death toll could be many thousands just in the city as more bodies are discovered every hour.
After long delays, hundreds of international aid workers set up makeshift hospitals and trucked in supplies on Saturday, 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.
Aid flown in to Tacloban's congested airport finally trickled into ravaged neighborhoods. Work crews and heavy equipment cleared debris from roadsides, but side streets remained piled with the sodden, tangled remains of homes.
In front of the San Fernando Elementary School, government workers distributed sacks of aid to a restless crowd of hundreds who had spent the last week camped in shattered wooden classrooms or in a main school building with floors covered in wet black sand. Nearby, about a dozen body bags were neatly lined up by the roadside.
Survivors living in the school said they had received little help since the disaster.
Rica Mobilla, an 18-year-old mother of one, said local authorities showed up two days after the disaster, handing out four kilograms of rice and a few packs of noodles for her family of thirteen. The family stretched this out with onions and garlic bought from the market.
"For the first two days after Yolanda, we didn't eat. After getting that packet, we eating once a day," she said, using the Philippine name for Typhoon Haiyan.
"I'm upset. I'm not blaming anyone. If there's aid there to give out we'll receive it."
President Benigno Aquino, caught off guard by the scale of the disaster, is scheduled to visit typhoon-affected areas on Sunday. 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.
In Tacloban the death toll is written on a whiteboard at City Hall and bodies have been buried in mass graves since Thursday. Tacloban mayor Alfred Romualdez said people may have been swept out to sea 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.
SURVIVORS START TO REBUILD, HOMELESS RISE
Relief officials reported a surge in desperate, hungry survivors trying to leave the coastal city of Ormoc, 105 km (65 miles) west of Tacloban.
"People are fleeing in mass numbers and coming to Ormoc, where they stand in line all day to get on a ferry only to be turned away," said Arnaldo Arcadio, an emergency responder with the Catholic Relief Services group.
"Ormoc is teeming with people who haven't eaten in days. They're hungry, thirsty and tired. They want to get out."
Across Tacloban, 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 number of people made homeless by the storm rose to 1.9 million, up from 900,000, the United Nations' humanitarian agency said. In Tacloban, at least 56,000 people face unsanitary conditions, according to the United Nations' migration agency.
Captain Victoriano Sambale, a military doctor who for the past week has treated patients in a room strewn with dirt and debris in Tacloban, said the pace of aid relief was rising.
"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."
U.S. HELICOPTERS AID RELIEF EFFORT
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.
British Prime Minister David Cameron on Saturday pledged 30 mln pounds for international aid agencies working in the Philippines.
But the patchy initial aid response highlighted the need for international agencies and local governments to prepare for more frequent, more devastating natural disasters, said Kristalina Georgieva, European Commissioner for International Cooperation, Humanitarian Aid and Crisis Response.
"This is a mindset change that must happen if we want to be able to stand up to this trend," she told Reuters in Tacloban.
U.S military assistance has been pouring into the Philippines since Thursday when the USS George Washington aircraft carrier and accompanying ships arrived off eastern Samar province, carrying 5,000 crew and more than 80 aircraft.
The Philippines is one of Washington's closest allies in Asia and a crucial partner in President Barack Obama's strategy of rebalancing U.S. military forces towards the region to counter the rising clout of China.
The Pentagon said on Friday that U.S. Navy amphibious ships will leave Okinawa in Japan "in the coming hours" carrying an additional 1,000 marines and sailors who will provide engineering equipment, relief supplies, and medical support.
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.
The U.S. military estimates that it delivered some 623,000 pounds (283,000 kg) of U.S. relief supplies to the Philippines so far. The American military also estimated that it had moved nearly 1,200 relief workers into Tacloban and airlifted nearly 2,900 displaced people from affected areas so far.
(Additional reporting by Rosemarie Francisco and Eric dela Cruz and Manuel Mogato in Manila, Michelle Nichols at the United Nations and Stephanie Nebehay in Geneva, Ranga Sirilal in Colombo; Writing by Jason Szep; Editing by John Mair and Michael Perry)
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