Relief efforts have been stepped up in Indonesia as three aid ships reached the worst-hit parts of the island chain devastated by Monday's tsunami.
Rescue teams are now at work on North Pagai island in the remote Mentawai Islands off western Sumatra.
More than 340 people are known to have died. Hundreds are still missing.
Indonesia's president has visited the islands, which were inundated after a 7.7-magnitude undersea earthquake triggered the tsunami three days ago.
President Susilo Bambang Yudhoyono cut short a trip to Vietnam to oversee the rescue effort, flying in a helicopter loaded with food and other basic necessities to the remote and inaccessible islands.
There he met both survivors and local officials, promising the central government would help West Sumatra's government to build temporary homes, health facilities and schools, his spokesman said.
The aid effort comes as Indonesia also struggles with the devastation caused by this week's eruption of Mount Merapi in central Java, which killed more than 30 people.
Local officials say most of the villages hit by the tsunami have been reached, with victims from the worst-hit areas being buried in mass graves.
But almost 400 remain unaccounted for, and rescuers are now working on the assumption that a large number of those missing will not be found alive, having been washed out to sea by the wave.
Although three aid ships carrying food, water, medical supplies and volunteers have now arrived in the disaster zone, bad weather and rough seas remain a major challenge to the relief effort, officials say.
Poor communications infrastructure are also making it difficult for aid teams to send in reports of damage.
The scale of the damage in the worst-affected communities is slowly emerging. Aerial images of the destruction taken from helicopters show survivors picking through debris-strewn roads and beaches littered with swollen bodies.
Relief workers have begun burying the victims, but lack the equipment needed to recover some bodies from beneath trees and debris.
Some villages were simply washed away by Monday's 3m (10ft) wave, and on South Pagai, the hardest-hit island, two villages were completely destroyed, said Hendri Dori Satoko, chairman of the Mentawai legislative council. No houses, government buildings or medical facilities remained standing.
He said most people had been fast asleep when the tsunami struck.
"People who managed to escape went to the mountains," he told the BBC. "Others are missing and presumed dead.
"Those who survived have nothing left except for the clothes on their body. They had to run and had no time to save their belongings."
Some survivors have been evacuated to North Pagai by speedboat, and the Mentawai Islands district chief, Edison Saleleubaja, said work would continue through the night to evacuate the injured for treatment at health clinics.
Thousands of refugees who lost their homes in the disaster have been moved into temporary shelters, says the BBC's Indonesia correspondent Karishma Vaswani.
The local government says it plans to set up a rehabilitation and reconstruction programme and move people away from the coastline where hundreds of houses were flattened, adds our correspondent.
The relief effort was limited, said Hartje Robert Winerungan, a spokesman for the National Disaster Management Agency, as helicopters and aid ships were taking hours to reach affected areas.
"Some villages in the remote island can't be reached so far," said Mr Winerungan. "We're working on it."
Search teams have found bodies strewn along beaches and roadsides as they scour the islands.
However, many are still looking for their loved ones, even as the fear grows that they will not find them alive.
Indonesian officials said locals had been given no indication of the coming wave, as a high-tech tsunami warning system installed in the wake of 2004's giant Indian Ocean tsunami was not working.
Two buoys monitoring rising water levels off the Mentawai islands had been vandalised and were out of service, officials told the BBC.
But even a functioning warning system may not have provided sufficient warning, as the epicentre of the earthquake was so close to the islands that residents had just a few minutes following the quake to escape to higher ground.
The vast Indonesian archipelago sits on the Pacific Ring of Fire, one of the world's most active areas for earthquakes and volcanoes.
More than 1,000 people were killed by an earthquake off Sumatra in September 2009.
In December 2004, a 9.1-magnitude quake off the coast of Aceh triggered a tsunami in the Indian Ocean that killed a quarter of a million people in 13 countries including Indonesia, Sri Lanka, India and Thailand.