More than 2550 have been hospitalised with serious injuries and 113 are missing after Friday's disaster, according to the National Disaster Management Agency spokesman Sutopo Nugroho.

"We expect the figures will continue to increase," he said on Wednesday.

More than 70,000 have been forced from their homes, he said.

Some of the injured were being evacuated as hospitals in the city of Palu suffered power outages, according to Bambang Sadewo, a military officer charged with the evacuation.

"They need treatment but because there's still no electricity, they can't be treated in Palu," he said.

Bambang added that 15 aircraft, including Hercules C-130 cargo planes, will be used to carry the injured to Makassar, the capital of South Sulawesi province.

At Palu's Mutiara Al Jufri Airport, injured victims were being treated in army camp beds, with some wearing leg and arm casts.

Rifki, one of the patients awaiting evacuation, said he and his wife had been severely injured in the earthquake.

"The ground below us suddenly moved like a blender and crushed our feet," he said. "There's no way we can get treatment here. There are no facilities or drugs. We have been given only painkillers."

Another survivor waiting to be evacuated, Basrun, said his wife was knocked unconscious during the earthquake and had still not woken up. "She has not undergone a scan," he said.

On Wednesday, rescuers found 10 bodies under the ruins of a collapsed eight-storey hotel, local news channel Metro TV reported.

Aid has begun to arrive after the disaster, however the pace remained slow due to damaged infrastructure.

President Joko Widodo, who visited Palu for a second time on Wednesday, said the government was doing all it could to bring aid to the victims.

"Food supplies have begun coming in, though not at maximum speed," Joko said, as he inspected a rescue effort at the Roa Roa hotel, where about 30 people were believed to be still trapped.

"Fuel and heavy machinery are coming in too and electricity is being repaired. Everything takes time," he said, appealing for patience.

The national disaster agency has said tents, food, water and sanitation facilities for more than 60,000 displaced people are in short supply.

Police have done little to stop outbreaks of looting. The government has played down the problem, saying victims could take essentials and shops would be compensated.

Australia promised to send more than 50 medical professionals to Indonesia to help as part of a $5 million aid package.

Elsewhere on Sulawesi island, the Mount Soputan volcano erupted on Wednesday, sending ash four kilometres into the sky, the national disaster management agency said.

There were no immediate reports of casualties and the ash was not considered a threat to aviation, Sutopo added.

The alert level for the volcano remained at one level below normal but "residents should be wary of the threat of mudflows, which can happen after an eruption," he said.

The 1785-metre-tall volcano last ejected ash plumes and searing gas in January and February 2016, after months of increased activity.

The volcano lies about 900km away from the area affected by the earthquake and tsunami.

Australian Associated Press