Siti Fadillah Supari, Indonesia's health minister, told the Reuters news agency that disease was becoming a concern, especially in Padang city.

"We are trying to recover people from the debris, dead or alive. We are trying to help survivors to stay alive. We are now focusing on minimising post-quake deaths," she said.

'Stretched to the limit'

Hundreds of doctors, nurses, search and rescue experts and cleanup crews have arrived at airport in Padang, bringing tonnes of food, tents, medicine, clean water, generators and a field hospital.

In depth

 
 Life on the Ring of Fire
 Responding to disaster
 Gallery: Sumatra rocked

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 Rescuers lack equipment
 Moment quake struck
 Rush to aid survivors
 Quake warning ignored

More than 30,000 homes, schools, mosques, hospitals and government offices have been flattened or severely damaged, a total of 17 per cent of all local infrastructure.

However, some shops reopened on Sunday and electricity was restored to parts of the town.

Others victims still require specialist treatment that overwhelmed medical facilities are struggling to provide.

"It's a tragic situation but the medical facilities here are really stretched to the limit," Patrick Fuller, a spokesman for the Red Cross, told Al Jazeera from Padang.

"They don't have some of the specialist equipment that they need for these kind of crush injuries, particularly where people have broken backs, they need to evacuated to specialist centres.

"We are hoping to get some more international teams in, possibly from Japan and Switzerland, who can support the government health services. But this is taking time and these people need treatment now."

Hundreds of doctors, nurses, search and rescue experts and cleanup crews have arrived at airport in Padang, bringing tonnes of food, tents, medicine, clean water, generators and a field hospital.

UN officials said that more tents and food were needed due to "huge levels of damage to infrastructure".

Villages 'swept away'

In outlying areas, where the full extent of the devastation is still being uncovered as rescue teams reach rural communities.

Many survivors are in desperate need of shelter, clean water and food [AFP]
"We are seeing some villages affected, some villages not so affected," Fuller said.

"It depends were they are located. If they are on a hillside the houses are down, a lot of the villages have been wiped out pretty much.

"Its patchy, it is still hard to say how many people have been killed in this disaster, but thousands of people have been affected, no doubt."

The Indonesian disaster management has confirmed that at least 809 people have been killed or are missing, but with up to 4,000 people believed to be trapped under the wreckage of their homes and workplaces the toll is expected to rise. 

Rescue teams and emergency aid are only just beginning reach these isolated villages, many of which were cut off by landslides.

Survivors are reported to have been forced to drink coconut water as their water sources are contaminated.