The United States, Australia and the United Nations are mobilising emergency aid to the Philippines as the scale of the devastation unleashed by Super Typhoon Haiyan emerges.

The Pentagon is sending military personnel and equipment to assist with the relief effort following the typhoon, which may have killed more than 10,000 people in what is feared to be the country's worst natural disaster.

"The United States is already providing significant humanitarian assistance, and we stand ready to further assist the government's relief and recovery efforts," US President Barack Obama said in a statement.

Some 90 Marines and sailors, and two KC-130J Hercules aircraft, left Japan for the Philippines on Saturday, with equipment including tilt-rotor aircraft which can operate without runways, Marines Colonel John Peck said.

The Australian government pledged Aus$10 million dollars (US$9.38 million), with Foreign Minister Julie Bishop describing the unfolding tragedy as "absolutely devastating" and on a "massive scale".

The sum includes Aus$4 million towards a UN global appeal and Aus$3 million for Australian non-government organisations. The aid will include tarpaulins, sleeping mats, mosquito nets, water containers and health and hygiene kits.

A team of Australian medics will leave on Wednesday via a C17 military transport plane from Darwin to join disaster experts already on the ground, the government said, after it disbursed emergency funds worth US$490,000 on Sunday.

Philippine rescue teams were said to be overwhelmed in their efforts to help those whose homes and livelihoods were destroyed after Haiyan ravaged large swathes of the archipelago Friday.

Officials were struggling to cope with the scale of death and destruction, with reports of violent looters and scarcity of food, drinking water and shelter.

United Nations leader Ban Ki-moon promised UN humanitarian agencies would "respond rapidly to help people in need".

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.

Pope Francis led 60,000 people in Sunday prayers for the Philippines, urging the faithful to provide "concrete help" to the largely Roman Catholic country.

"Sadly, there are many, many victims and the damage is huge," he said.

Other aid mobilised for the Philippines includes:

-- The European Commission said it would give three million euros ($4 million) towards the relief efforts.

-- Britain offered an emergency support package worth $9.6 million. Germany's embassy in Manila said an initial shipment of 23 tonnes of aid was being flown in and German rescue teams were already at work.

-- Like Australia, New Zealand also increased its humanitarian relief on Monday, bringing its total to NZ$2.15 million (US$1.78 million), while Canada has promised up to US$5 million to aid organisations.

-- Medecins Sans Frontieres (Doctors Without Borders) said it was sending 200 tonnes of aid including medicine, tents and hygiene kits to arrive mid-week, with the first cargo plane leaving from Dubai on Monday and another from Belgium on Tuesday.

-- Taiwan's government pledged immediate cash aid of US$200,000 and the Singapore government donated US$40,000.

-- Oxfam, the British-based relief organisation, said it has sent an assessment team ahead of aid operations.

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