(Photo: REUTERS / Erik De Castro)Typhoon survivors, waiting to leave the province of Leyte in the aftermath of the Super Typhoon Haiyan, are pictured in the hold of a C-130 military transport plane at Tacloban airport, in central Philippines, November 15, 2013. The death toll from the powerful typhoon that swept the central Philippines nearly doubled overnight, reaching 4,000, as helicopters from a U.S. aircraft carrier and other naval ships began flying food, water and medical teams to ravaged regions.

TACLOBAN, Philippines (Reuters) - Survivors of Typhoon Haiyan flocked to ruined churches on Sunday, kneeling in prayer under torn roofs as the Philippines faced an enormous rebuilding task from the storm that killed at least 3,681 people and displaced 4 million.

At Santo Niño Church, near the waterfront in the flattened city of Tacloban, birds flitted between the rafters overhead as women moved through the pews with collection plates. At the end of mass, the Roman Catholic congregation broke into applause.

Rosario Capidos, 55, sat crying in one row, hugging her nine-year-old grandson, Cyrich.

Capidos had been sheltering at home with nine other members of her family when Haiyan struck on Nov. 8. As the waters rose, she floated her three grandchildren on a slab of styrofoam through a road flooded with debris and shipping containers to a nearby Chinese temple. Her family survived.

"That's why I'm crying," she said. "I thank God I was given a second chance to live."

A massive relief effort is finally kicking into gear, nine days after one of the most powerful typhoons on record wreaked havoc across the impoverished area in the central Philippines with monster winds and a deadly storm surge of sea water.

Philippine authorities and international aid agencies face a mounting humanitarian crisis, with the number of people displaced by the catastrophe estimated at 4 million, up from 900,000 late last week.

Nearly half a million houses were damaged by the storm, half of them destroyed, according to the United Nations.

While aid packages have begun to reach more remote areas, much of it carried by helicopters brought by the USS George Washington aircraft carrier, the United Nations said people were still going hungry in some mountainous provinces.

It said information about several provinces in the west of the Visayas region remained "limited", with 60 percent of people in towns in the northeast part of Capiz province needing food support.

"I remain concerned about the health and well-being of the millions of men, women and children who are still in desperate need," U.N. humanitarian chief Valerie Amos said in a statement.

President Benigno Aquino, caught off guard by the scale of the disaster, is scheduled to visit 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.

There are 1,186 people missing, according to the national count. The official death toll has only risen by 60 since Friday, giving hope that initial local estimates of 10,000 dead were overstated.

The government estimated damage to infrastructure and agriculture at about 10 billion pesos ($230 million), the bulk of it in the farming sector. The United Nations warned that economic and human cost could rise if aid did not reach farmers in rice-growing regions in time for the next planting season in December and January.

It also said that fishing, another crucial food source, had been placed in jeopardy by the storm.

"The destruction of boats, fishing gear, fish ponds and related equipment left many families with no means of livelihood and decreased protein intake," the U.N. Office for the Coordination of Humanitarian Affairs said.

(Writing by Stuart Grudgings; Editing by John Mair)