Jakarta: Rescue workers were racing against time on Friday in their search for hundreds of people still missing on Indonesia's tsunami-hit Mentawai islands, as an official estimated that the death toll could rise to around 600.
Storms and waves as high as six metres have prevented aid supplies from reaching some areas in the Mentawai chain, said Ade Edward, head of the Regional Disaster Management Agency in West Sumatra province, of which the Mentawais are part.
Edward said the death toll from Monday's magnitude-7.7 earthquake stood at 394, while 312 people were listed as missing and more than 400 were injured.
But he estimated that only about 100 of the missing were still alive.
"We are assuming that one third of the missing are in the hills but have not been accounted for by local officials," he said.
"The others were perhaps swept away by the sea or buried under the mud," he added.
Edward said authorities were preparing to airdrop supplies using helicopters.
"We have to do the best we can," he said. "We must not allow the weather to prevent aid supplies from reaching those who need them."
West Sumatra Governor Irwan Prayitno said there was an urgent need for more rescuers and speed boats to assist with collecting the bodies and getting aid to the survivors in the worst-hit Pagai Selatan and Pagai Utara districts, which were only reachable by sea.
The Kompas daily reported on Friday that in Pagai Utara's Betumonga village, only 50 villagers from a population of around 260 survived.
Monday's quake displaced more than 4,000 people and damaged hundreds of homes and buildings, as well as telecommunication links, roads and bridges.
Rescue workers appealed for more body bags, fearing outbreaks of disease if the bodies were not collected quickly.
In September 2009, a magnitude-7.6 earthquake hit Padang and neighbouring districts in West Sumatra, killing more than 1,100 people.
Indonesia sits on the Pacific Ring of Fire, where continental plates meet, causing earthquakes and volcanic eruptions.