The number of people believed missing from the quake and tsunami that struck Indonesia's Palu city has soared to 5,000, an official said Sunday, an indication that far more may have perished in the twin disaster than the current toll.

Indonesia's disaster agency say they have recovered 1,763 bodies so far from the 7.5-magnitude and subsequent tsunami that struck Sulawesi on September 28.

But there are fears that two of the hardest-hit neighbourhoods in Palu -- Petobo and Balaroa -- could contain thousands more victims, swallowed up by ground that engulfed whole communities in a process known as liquefaction.

“Based on reports from the (village) heads of Balaroa and Petobo, there are about 5,000 people who have not been found,” agency spokesman Sutopo Purwo Nugroho told reporters Sunday.

“Nevertheless, officials there are still trying to confirm this and are gathering data. It is not easy to obtain the exact number of those trapped by landslides, or liquefaction, or mud.”

Nugroho said the search for the unaccounted would continue until October 11, at which point they would be listed as missing, presumed dead.

The figure drastically increases the estimates for those who disappeared when the disaster struck 10 days ago. Officials had initially predicted some 1,000 people were buried beneath the ruins of Palu.

But the latest tally speaks to the considerable destruction in the worst-hit areas of Petobo and Balaroa as the picture on the ground has become clearer.

Wiped out

Petobo, a cluster of villages in Palu, was virtually wiped out by the powerful quake and wall of water that devastated Palu.

Much of it was sucked whole into the ground as the vibrations from the quake turned soil to quicksand.

It was feared that beneath the crumbled rooftops and twisted rebar, a vast number of bodies remain entombed.

In Balaroa, a massive government housing complex was also subsumed by the quake and rescuers have struggled to extract bodies from the tangled mess in the aftermath of the disaster.

The government has been considering declaring those communities flattened in Palu disaster as mass graves, and leaving them untouched.

Hopes of finding anyone alive have faded, as the search for survivors morphs into a grim gathering and accounting of the dead.

“This is day ten. It would be a miracle to actually find someone still alive,” Muhammad Syaugi, the head of Indonesia's search and rescue agency told AFP on Sunday.

'Great need'

The grim news comes as relief efforts were ramped up to reach 200,000 people in desperate of help after days of delays.

Looters ransacked shops in the aftermath of the disaster more than a week ago, as food and water ran dry and convoys bringing life-saving relief were slow to arrive.

But the trickle of international aid to Palu and local efforts to help the survivors have accelerated in recent days.

Planeloads of supplies were landing with increasing frequency in Palu, where daisy chains of troops unloaded supplies directly onto trucks or helicopters.

More than 82,000 military and civilian personnel, as well as volunteers, are on the ground while Indonesian army choppers are undertaking supply runs to remote areas blocked off by the disaster.

“They are in great need because the road is cut off and it's accessible only by air”, Second Lieutenant Reinaldo Apri told AFP after piloting a chopper to rugged Lindu district, some 40 kilometres (25 miles) south of Palu.

Hercules planes carrying tonnes of donations from Australia and the United States reached Palu on Sunday morning, as did a plane chartered by Save the Children and another carrying a South African medical team.

Teams of Indonesian Red Cross workers set up warehouses and fanned out to distribute supplies across the region.

But relief workers face a monumental task ahead.

The tens of thousands left homeless by the disaster are scattered across Palu and beyond, many squatting outside their ruined homes or bunkered down in makeshift camps and entirely dependent on handouts to survive.

“There is nowhere else to get food, nowhere is open,” said 18-year-old Sela Fauziah in Palu's central market, where she queued with hundreds for essential food items being distributed by soldiers.

Things are even more desperate in remoter areas.

“I am coming to Palu to report that we need tents, because 95 percent of our village has been destroyed,” said Simsom Mudju from Lindu, who clambered aboard the chopper to tell the outside world about his marooned community's plight.