US and British vessels were heading to the Philippines as the UN appealed for aid amid the large-scale devastation caused by Typhoon Haiyan.
The US has deployed an aircraft carrier and navy ships to the Philippines, while the UK is sending a naval destroyer.
At least 10,000 people are feared to have been killed, and thousands of survivors desperately require aid.
Philippine President Benigno Aquino has declared a state of national calamity.
In a statement, he said the two worst affected provinces, Leyte and Samar, had suffered massive destruction and loss of life.
A huge international relief effort is under way, but rescue workers have struggled to reach areas cut off since the storm.
UN Secretary General Ban Ki-moon described images of the impact of the storm as “heartbreaking”.
The UN would launch a large-scale humanitarian plan, and allocate $25m (£15.5m) “to fund critical relief efforts”, he said.
“Many thousands of people are reported to have died and almost 10 million people have been affected… Let us all show our solidarity with the people of the Philippines at this time of need,” he added.
“One shirt. That’s all I’m asking for”: The BBC hears survivors’ stories
The BBC’s George Alagiah reports from a makeshift distribution centre at Manila airport
One of the most powerful storms on record to make landfall, Haiyan – named “Yolanda” by Philippine authorities – struck the coastal provinces of Leyte and Samar on Friday.
It then headed west, sweeping through six central Philippine islands.
Air Force Capt Antonio Tamayo told AP news agency the scene in Tacloban, one of the worst-hit areas, was “overwhelming”.
`We need more medicine. We cannot give anti-tetanus vaccine shots because we have none.”
Officials said looting was widespread and order was proving difficult to enforce. Correspondents say many ordinary people are simply scavenging for the food and water needed to survive.
In a statement, the US said that aircraft carrier USS George Washington and other navy ships should arrive in the Philippines “within 48-72 hours”.
“As needed, 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 statement said.
UK Prime Minister David Cameron announced that the Royal Navy destroyer HMS Darling would soon head to the disaster zone from Singapore.
It would take five days to arrive but once in the Philippines brings engineering and first aid expertise as well as the use of a Lynx helicopter.
Other countries have also pledged millions of dollars in assistance. Australia has approved $9m in humanitarian aid to the Philippines, while New Zealand has pledged over $1m.
Reports from Tacloban say soldiers have been distributing food and water to some residents and the US military has sent marines to the city.
A Philippine military spokesman was quoted as saying on Monday that 942 people had died in the typhoon’s aftermath, though it is clear the official death toll will rise significantly.
UN humanitarian official John Ging said: “Many places are strewn with dead bodies”.
“The first priority of response teams, once they were able to navigate their way into these areas, is to mobilise the burial of dead bodies because of the public health issues,” he said.
“As we get more and more access we find the tragedy of more and more people killed in this typhoon,” he added.
More than nine million people have been affected in the Philippines. Many are now struggling to survive without food, shelter or clean drinking water.
A picture is slowly emerging of the full damage wrought by the storm:
- The exposed easterly town of Guiuan, Samarprovince – population 40,000 – is said to be largely destroyed
- Three-hundred people were killed in the town of Basey, also in Samar, the provincial disaster office confirmed
- Tacloban, Leyte province, was largely flattened by a massive storm surge and scores of corpses are piled by the roadside, leaving a stench in the air as they rot. Hundreds of people gathered at the airport desperate for food and water, others trying to get a flight out
- Disaster worker Dennis Chong told the BBC that assessments in the far north of Cebuprovince had shown some towns had suffered “80-90% damage”
- Baco, a city of 35,000 in Oriental Mindoroprovince, was 80% under water, the UN said.
Some are questioning what more authorities could have done to prepare for this, just the latest in a string of disasters to hit the nation of more than 7,000 islands.
Authorities had evacuated hundreds of thousands of people before the typhoon arrived, but many evacuation centres – schools, churches and government buildings – proved unable to withstand the winds and storm surges.
Haiyan brought sustained winds of 235km/h (147mph), with gusts of 275 km/h (170 mph) and waves as high as 15m (45ft). In some places, as much as 400mm (15.75 inches) of rain fell.