US and British warships were deployed Tuesday to the typhoon-ravaged Philippines where well over 10,000 people are feared dead and countless survivors are begging for help in rain-soaked wastelands.

Four days after Super Typhoon Haiyan destroyed entire coastal towns in mostly poor central islands with record winds and tsunami-like waves, the magnitude of the disaster continued to build with almost unimaginable horror.

"We are certainly expecting the worst. As we get more and more access we find the tragedy of more and more people killed in this typhoon," UN humanitarian operations director John Ging said, after Philippine President Benigno Aquino declared a "state of national calamity".

The United Nations warned 10,000 people were feared dead in just one city, Tacloban, the provincial capital of Leyte province where five-metre (16-foot) waves flattened nearly everything in their path as they swept hundreds of metres (yards) inland.

Nearly 10 million people, or 10 percent of the Philippines' population, have been affected, while 660,000 have lost their homes, the UN estimated as it launched a flash appeal to raise hundreds of millions of dollars for a relief effort.

Overwhelmed and under-resourced rescue workers have been unable to provide desperately needed food, water, medicines, shelter and other relief supplies to many survivors, and desperation has been building across the disaster zones.

"There is nothing here left for us. Our house is gone, we don't have any money, we don't have our documents, passports, school records," Carol Mampas, 48, told AFP at Tacloban's destroyed airport as she cradled her feverish baby son in a blanket.

"Please, please, tell authorities to help us. Where is the food, where is the water? Where are the military collecting the dead?"

Bodies still litter the wreckage, while security concerns are building as gangs take advantage of a security vacuum to loot homes and businesses that survived the typhoon.

The government announced a night-time curfew for Tacloban and deployed special forces across the ruined city in a bid to prevent looting.

Downpours worsen desperation

Heavy rain overnight in Tacloban compounded the survivors' desperation, while a tropical storm to the south threatened other typhoon-hit islands where hundreds of other people were also killed.

An international relief effort has begun to build momentum, with the United States and Britain announcing they would quickly deploy warships carrying thousands of soldiers to the Philippines.

The Pentagon said the aircraft carrier USS George Washington, which has 5,000 sailors and more than 80 aircraft aboard, will head to the United States' close Asian ally on Tuesday, from Hong Kong where it is currently on a port visit.

Five other warships are also being deployed, and the group is expected to reach the Philippines within two to three days, the Pentagon said. Ninety US marines arrived in Tacloban on Monday as an advance team.

"These ships and aircraft will be able to provide humanitarian assistance, supplies, and medical care in support of the ongoing efforts led by the government and military of the Republic of the Philippines," the Pentagon said.

Britain will also send a warship, currently deployed in nearby Singapore, "at full speed" to the Philippines, Prime Minister David Cameron announced on Monday.

Many other countries have pledged help with even China, which has been embroiled in a bitter territorial dispute with the Philippines, offering aid and sympathy.

The UN children's fund UNICEF said a cargo plane carrying 60 tonnes of aid including shelters and medicine would arrive in the Philippines Tuesday, to be followed by deliveries of water purification and sanitation equipment.

The UN refugee agency, UNHCR, was also organising an airlift carrying aid including hygiene kits.

Aquino's declaration late Monday of a state of calamity allowed the government to impose price controls and quickly release emergency funds.

"In the coming days, be assured: help will reach you faster and faster," he said in a televised address.

"My appeal to you all is: remaining calm, praying, cooperating with, and assisting one another are the things that will help us to rise from this calamity."

Coastal towns reduced to piles of wood

Haiyan's sustained winds when it hit Samar island, where it first made landfall, reached 315 kilometres (195 miles) an hour, making it the strongest typhoon in the world this year and one of the most powerful ever recorded.

Aerial photos of Samar showed whole districts of coastal towns reduced to piles of splintered wood.

The official government death toll stands at 1,774, although authorities have admitted they have not come close to accurately assessing the number of bodies lying amid the rubble or swept out to sea.

The advance US marines expressed shock at the scale of the disaster after getting a bird's eye view flying into Tacloban aboard C-130 transport aircraft full of relief supplies.

"Roads are impassable, trees are all down, posts are down, power is down.... I am not sure how else to describe this destruction," Brigadier General Paul Kennedy, the commanding general of the Okinawa-based 3rd Marine Expeditionary Brigade, told reporters.

The Philippines is hit with an average of 20 tropical storms or typhoons a year, as they emerge from the Pacific Ocean and sweep west.

However Haiyan's record intensity has fuelled concerns that climate change is increasing the ferocity of storms.

Blaming global warming for Haiyan's mega-strength, Philippines negotiator Naderev Sano pledged at UN climate talks in Warsaw on Monday to fast until progress was made on tackling the environmental crisis.

If the death toll of more than 10,000 is correct, Haiyan would be the deadliest natural disaster ever recorded in the country, exceeding the 1976 Moro Gulf tsunami that killed between 5,000 and 8,000 people.

Haiyan swept out into the South China Sea on Saturday and hit Vietnam and China on Monday in a significantly weakened state, although still strong enough to uproot trees and tear roofs off hundreds of homes.

At least seven people were reportedly killed in China.