Grieving survivors of a monster typhoon that smashed into the mainly Catholic Philippines flocked to shattered churches Sunday, as aid workers intensified efforts to reach desperate survivors in remote communities.

Residents of one isolated village jostled each other and strained their arms upwards against the powerful downdraft from a helicopter as it hovered just feet above them with boxes with food, television footage showed.

The cartons were pushed from the chopper, setting off a frenzied scramble, as the villagers tore apart the packing and scurried away with the contents.

The helicopter was from the USS George Washington aircraft carrier, which has galvanised the initially slow aid operation since it arrived Thursday. It immediately began airlifting large volumes of relief supplies to inland airstrips and hard-to-access communities.

Many still face a daily battle for survival after the November 8 super-storm, packing some of the strongest winds ever recorded, ripped their world apart.

The United Nations raised its estimate for the number of people displaced from 1.9 million to 3.0 million, while the official death toll rose to 3,976 with 1,590 people missing.

The enormous international relief operation picked up momentum over the weekend, bringing food, water and medical supplies and airlifting basic necessities to remote mountainous areas.

President Benigno Aquino, who has been criticised for the slow speed of his government's response, called for understanding as he toured some of the worst-hit areas Sunday.

"Please have patience. These affected areas are really spread out," Aquino said, while acknowledging that more needed to be done.

The president said he would remain in the affected area for several days, or until he was "satisfied" the situation had improved.

The church services offered a brief respite from the misery.

About 300 people in Guiuan, the first town to be hit by Super Typhoon Haiyan, attended Sunday mass in the courtyard of the ruined 400-year-old Immaculate Conception church, whose damaged bells had to be rung by striking them with an iron bar.

Father Arturo Cablao commended the community's strength of spirit, as parishioners -- some of them silently weeping -- stood among twisted roofing sheets, glass shards and mud.

About 80 percent of the Philippines' 100 million people are Catholic, a legacy of Spanish colonial rule, and their steadfast faith was on display throughout the central islands devastated by Haiyan.

"If there is no God, who else is there? He is our only hope," Bibeth Sabulao told AFP after she received communion in Guiuan.

In Tacloban, one of the hardest-hit cities, hundreds of devotees sat on flood-soaked pews attending mass at the 124-year-old Santo Nino church, which had its roof ripped off by Haiyan's ferocious winds.

Relief effort builds

As the morning services were held, the international relief effort continued to build, consolidating its initially tenuous grip on the catastrophic situation.

"The arrival was pretty slow at first but it is picking up extremely well," World Food Programme emergency coordinator Samir Wanmali told AFP at Tacloban airport.

A British warship, HMS Daring, arrived on Sunday, and was to be followed by the helicopter carrier HMS Illustrious.

The United Nations and other relief workers say the death toll will climb much higher over the coming months as a full assessment is made of the 600-kilometre (380-mile) stretch of islands hit by Haiyan.

If the worst fears are realised, Haiyan could be the country's deadliest natural disaster, surpassing the 1976 Moro Gulf tsunami that killed between 5,000 and 8,000 people on the southern island of Mindanao.

Dramatic video footage emerged showing the destructive size and power of the typhoon's storm surge as it slammed into the Samar coastal town of Hernani, engulfing and sweeping away houses.

"It was like a huge tsunami," said Nickson Gensis, a staff member of the child development agency Plan International who recorded the surge from the second floor of a house that withstood the impact.

UN Secretary General Ban Ki-moon said Saturday that the super typhoon was an "urgent warning" to mankind of the consequences of climate change.

Although many devotees in the Philippines sought solace in their churches, for some the disaster was proving a severe test of their faith.

Father Edwin Bacaltos, the parish president at the Redemptorist Church in Tacloban, told AFP that people had repeatedly asked him why the catastrophe had occurred.

"But this is not God's punishment. I have told them that God still loves us. He will not abandon us," Bacaltos said.