Eyewitnesses said only a few houses were left standing after the side of a mountain collapsed early on Friday, sending a torrent of mud and boulders into the village of Guinsaugon on the island of Leyte.
"There are about 1500 missing, 200 dead," Richard Gordon, the head of the Philippine Red Cross, said in a radio interview.
"We're hoping for the best but preparing for the worst," he said.
The first footage from the devastated village showed a sea of mud covering what had been lush green valley farmland. The mud was estimated to be at least six metres (yards) deep.
Only a few sheets of tin roofing and the occasional coconut tree could be seen.
Tiny groups of mud-spattered survivors walked through the muck, stunned by the scope of the destruction.
Among those feared buried in the mud were nearly 250 children and adults in the village school, officials said. Experts blamed deforestation for the tragedy, which came after days of rainfall that was five times higher than usual.
In a televised address to the nation, Gloria Arroyo, the Philippine president, said rescue teams were rushing to the area from "air, land and sea" to cope with the catastrophe.
Some 250 school children are
feared buried in the mud
"I have ordered the Coast Guard and our entire naval force in the (central Philippines) region to the area," she said. "Naval ships will be used as floating hospitals and command centres for relief and rescue."
The international community led by the US offered assistance while the Red Cross in Geneva appealed for two million Swiss francs to fund a relief operation.
It appealed to donors to come forward fast as it needed to provide temporary shelters, mosquito nets, medical supplies and other aid for survivors.
The United States sent two military ships to the stricken area to help and will look at other ways to provide urgently needed help, the White House said.
"The US has received a request from the Philippine government and will provide resources today to help fund the immediate response. US military assets, in the form of two ships currently in the Philippines, are also being dispatched to the area," said spokesman Trent Duffy.
US and Philippine forces have been taking part in joint military exercises in this country in recent days. "We hope and pray that ongoing search and rescue operations will help save as many lives as possible," Duffy said.
Leyte Governor Rosette Lerias said the last census showed there were 375 houses with 3000 people living in Guinsaugon before the landslide. She described the village as totally flattened.
President Arroyo promised
speedy rescue and recovery
"It was like mud running down the mountain and it covered the village in seconds," she said, quoting survivors. Lerias said many Guinsaugon residents had been evacuated after landslides earlier in the week had killed more than 20 people on Leyte, but that many had returned on Friday because the rains had stopped and the sun had come out.
A mild 2.6-magnitude earthquake which struck before the landslide may also have helped set off the wall of mud that crashed down on the village, said Rene Solidum, head of the government vulcanology office.
"The area could have really been ready for a landslide because of the amount of rainfall and if there was a minor earthquake, it might have hastened it," Solidum said.
Rescue and recovery
Army Colonel Nestor Sadirin, head of a rescue task force, said 16 bodies had been recovered so far and 100 people rescued.
Gordon said the Red Cross would dispatch sniffer dogs to hunt for survivors.
"This is one of the most remote and inaccessible regions of the country. The mud is waist-deep in some areas and this is making it very difficult to search for survivors and get help to the injured," he told reporters.
"This is one of the most remote and inaccessible regions of the country...this is making it very difficult to search for survivors"
Military helicopters were able to reach the area despite heavy clouds but the flights ceased after nightfall because the aircraft did not have night-flying capabilities.
Much of the rescue effort had to be called off after nightfall because there were no lights and because "the soil was very unstable", said civil defence spokesman Anthony Golez.
Relief groups called for drinking water, food, blankets and body bags to be brought to the scene. More than 5000 people were killed in a combined flood and mudslide on Leyte in November 1991.